Towards a virtual piano action
This article first appeared in
magazine. In it, the author reports on an Artists and New Technology
design and build a computer-controlled piano action.
Piano Music in Evolution
Since the turn of the century music for the piano has exploded
with stylistic diversity and performance innovation. This has
largely taken place where the inherent qualities of the
instrument and their potential have been recognised and promoted.
Not only in the West but in countries such as Japan, China and
Korea, enthusiasm is manifest through performance, manufacturing
and the fostering of study and social awareness through music
schools and methodologies (Yamaha, Suzuki, etc). The instrument's
historical repertoire (essentially from the Viennese classics to
early Twentieth century) continues to feature prominently in most
assessments of the instrument. However, it is clear that through
many unique social and technological changes, its musical
potential is being exploited by a far wider and larger cross
section of world societies. This is evident, for example, in the
scope of discussion in popular keyboard magazines. It may also be
assumed that the process is continuing under the influences of
In certain musical idioms, particularly those in the aural
tradition such as Jazz, Blues, Rock, etc, piano technique has
changed through the dissemination of recordings as well as
through direct contact with the current influential
practitioners. The dissemination of recorded music has supported
many enthusiasts who, by emulating the definitive performers,
have themselves developed further distinctive techniques. In a
genre of music that appears to be less constrained by formalism
and pedagogy, imitation becomes an underlying reactionary force
that stems the tendency for particular styles to disintegrate as
quickly as they emerge.
The situation in the Art music world - as distinct from other
musical milieus: commercial, popular, etc - is somewhat different
because most performers are bound to interpret some form of
score. In this notated representation of the music, technical as
well as stylistic innovation is dependent on the composer's
practical and theoretical knowledge of the instrument. Thus, the
success of music composed in this manner is largely attributable
to the perspicacity of the composer in the treatment of both
instrument and performer. This is evident in such works as the
prepared piano works of John Cage; the
works of Karlheinz Stockhausen; Charles Ive's
; Elliott Carter's
; the Player Piano
of Conlon Nancarrow and many others from the twentieth century
Recorded music is perhaps less influential as a conveyance for
imitation in an art music context because direct imitation is not
explicitly part of the evolution of that musical genre. However,
recordings are evidence of the success of a musical idea and
convey proof that certain compositional ideas work (or don't).
Furthermore, the quality of contemporary music performance and
interpretation has improved through its general availability in a
recorded form. Those interested in contemporary music are able to
further familiarise themselves with it between performances.
Recordings also tend to establish personal criteria through which
a comparison can be made between the memory of the recordings and
live performances or other recordings. The ease with which it is
possible to compare one interpretation of a work with another or
one style with another, must contribute to a broadening of
musical perspective and at least, perhaps introduces avenues for
Underlying the piano's social ethos throughout this century is
the fact that the instrument had reached evolutionary stasis by
the end of the nineteenth century. The following is a summary of
the significant developments of last century (Grover 1973.
Certainly, since last century the piano has undergone
considerable refinement in component materials and production
techniques yet it has essentially remained an instrument of 19th
century technical achievement. It is perhaps, possible to
attribute a considerable part of the diversity of piano music
this century to developmental stability. Unlike the current state
of electronic musical instruments, musical innovation is entirely
up to the performer; the manufacturer has no part in encouraging
new music other than through promoting artists who use their
1821. Sebastien Erard produced the 'repetition action' with
1826. Jean-Henri Pape patented felt hammers.
1843. Jonas Chickering patented the first one-piece cast-iron
frame for a grand piano.
1859. Steinway produced the first over-strung grand piano.
1874. Steinway perfected the 'sostenuto' pedal.
This illusion of stability should not be interpreted in the first
instance as an attainment of technical perfection. Given human
nature and art, this is, of course, intrinsically impossible. The
instrument, however, remains relatively constant in appearance
and sound because of its social prominence and musical tradition.
In order to remain a worthy interpreter of the historical
repertoire as well as the piano music of tomorrow, the impact of
even minor technical modifications and improvements are generally
vetted against the standard repertoire, performance criteria and
contemporary musical expectations. Transitions from wood or
ivory to plastic, or from iron to alloys, do not significantly
affect the perpetuity of the piano repertoire and are eventually
accepted without regret. Yet the sum of the many minor changes
must ultimately be manifest as an evolutionary step, even if
obscured by the passing of many years.
Although it is difficult to clearly define the relationship
between instrument evolution and musical style, music itself
should not be assessed on the basis of technical progress. As
Willi Apel pointed out:
"Nothing is more dangerous and misleading in the study of the
arts than to regard achievements of the past from the standpoint
of technical progress. A superficial observer sees only what has
been gained in the fight and not what has been lost. The true
historical mind, however, sees that in the history of humanity
there is no possibility of perfection, and that there is only a
faint hope of approaching it." (Apel 1953. p.86)
To some extent the continuing popularity of the piano repertoire
of the 18th and 19th centuries is attributable to the fact that
its performance has been widely accepted on contemporary
instruments. Those with an understanding of the historical
instruments would argue that certain original qualities of the
music are consequently lost or misrepresented. This may very well
be true but for the most part the musical intention and
aesthetics are present where the interpretation is sincere and
This concern for historical accuracy has increased with the
growth in popularity and scholarship of pre-baroque music this
century. It has fuelled the underlying controversy and debate
over, not only the use of authentic replications of historical
instruments but musical practice and interpretation researched
from primary sources. Stepping back from the issues surrounding
early musicology, the net effect of this debate is perhaps to
increase the musical public's awareness of instrumental diversity
and evolution. If there is greater awareness of a musical
continuity then contemporary instrumental practices should appear
less disconnected from tradition.
The technical evolution of musical instruments is, of course,
inevitable. What is perhaps different today is the nature of the
association that is formed between the various instruments and
the current musical styles. As the instruments themselves become
'virtual', that is able to adopt the characteristic sounds and
behaviour of many other instruments, the relationship between
instrument and musical idea that is not only difficult to define
but transient. Combine this with the rate with which 'new'
instruments are appearing on the market and the result is a
instrument/music relationship that has never existed
The Action Project in abstract
In 1987 I began to consider the design and development of a high
performance electro-mechanical action for a grand piano. The
opportunity arose through the Artists and New Technology Program
from the Australia Council. The concept had been maturing from
the early 1980's when I first began working with pianos under
microcomputer control. During those interim years, composition
and research with less ambitious instruments and equipment
(Riddell 1982, 1988) helped clarify my future intentions,
aesthetics and the inevitable pragmatic considerations
associated with the project.
When construction seemed imminent, expectations of the function
of the action were largely influenced by the prospect of an
unusual Performer/Machine Interactive system. One that could
exploit a distinct relationship between the piano tradition and
digital technology. At that time it was felt that mainstream
music technology was not pursuing the same type of instrumental
relationship in such a simple and direct manner. On a fundamental
level, the difference is manifestly the acoustic production
sound, while at a higher level, it is performance on a familiar
instrument with an entirely different philosophy towards its
An integral part of the action's functionality allows it to be
used in two performance contexts. In the first, it can operate
through a live performer in real-time. In the second, by the
computer alone, that is without any real-time human
intervention. This range of functionality covered my interests in
real-time performance and algorithmic composition.
From the perspective of a performer/machine interactive system,
the action can be regarded as 'virtual' in that the performer's
actions can be mapped to almost any pitch/rhythm combination on
the instrument. Transposition, inversion and intervalic
parallelism with all or partial input are some of the simple
processing functions possible for keyboard actions. The more
fascinating possibilities lie beyond these techniques where
performer input is mapped to parameters other than pitch or
rhythm. In fact they might not be parameters but functions.
The action has also a degree of operational autonomy that the
traditional action could not possibly accommodate. The
relationship between a hammer and its associated damper is
flexible. They can operate synchronously or under separate
control which permits two timbral possibilities: playing with the
damper off or playing with the damper on the string.
Although the prospects for the research and performance of the
action appear limited, it is an attempt to alleviate the
difficulties of working with computer technology and acoustic
instruments. To begin with the grand piano is a complex and yet
ideal medium that is reasonably available at most performance
venues. With the action in a modular state, the logistics of
performing are considerably reduced. However, installing and
adjusting the action will still take some time but does not
require the piano to be altered or modified in any way other than
the removal of the original action. This is a straightforward
operation which takes only a few minutes.
Initial Research and Observations of the Traditional Grand Piano
Action and the Proposed Action
The preliminary research towards the project began in mid 1987 in
the Department of Physics at La Trobe University
. This initial
research was not directed towards the immediate construction of
the new action but an examination of the physical behaviour of
the traditional grand piano action. The research was conducted
jointly with Dr Michael Podlesak
and centred around the
measurement and investigation of the velocity, acceleration and
power in a hammer when propelled into motion. Experiments were
carried out using an ONO SOKKI FFT (Fast Fourier Transform)
analyser. This instrument recorded, calibrated and plotted values
that were transmitted to it from a tiny accelerometer mounted on
the hammer shank.
The information gathered from the experiments was used to convert
the hammer's mechanical energy into electrical energy. The power
in the hammer motion was quantifiable in terms of Watts and these
values could be used comparatively with the electronic solenoids
also under examination.
The results finally revealed that, within certain limitations,
the physical size and power rating of the proposed hammer
solenoids would be acceptable. This was particularly important
because it meant that the existing Pianocorder solenoids and
control components could be used, thus reducing the cost and
complication of the overall system. The major restrictions,
however, arose in relation to the adequacy of the power supply
from a standard domestic source (2400 - 3000 watts) and whether
the solenoids would be capable of an effective dynamic range in
considerably less than optimal conditions.
The experiments on the instrument focused on two dynamic ranges:
moderately loud and extremely loud and the differences between
human and electro/mechanical performance for this experimental
range was considered from a number of perspectives.
The more demanding end of the performance spectrum was of more
interest since the lower end is demonstrably less problematic
for either system, attention could therefore be directed towards
the extreme case to at least establish a possible upper limit.
The experiments at this dynamic level revealed that the power in
terms of electrical energy was approximately equivalent to 25
watts. However, the occasions for such extreme performance (if
any) are only likely to be found in later twentieth century music
and even then, in order to achieve such a dynamic, the performer
would generally have to forgo speed, elegance and repetition for
brute strength. It might be expected that even the most extreme
contemporary works would not require the performer to sustain or
distribute this sort of power to large groups of notes over a
considerable time. Neither is it possible to apply such power to
complex passages with any degree of subtlety or accuracy
(although the Jazz musician Cecil Taylor might come close to
being an exception).
It has been speculated that the experimental solenoids could take
an equivalent power (25 watts) and possibly deliver the same
effect. As desirable as it may be to emulate this level of
performance, it is doubtful that the existing solenoids and
support electronics could sustain repeated use under such
conditions and also whether many of them could be supplied from
a domestic source. This result was eventually considered too
extreme to pursue as necessary for the electro-mechanical system
yet it helped to define a practical upper limit.
The moderately loud attack resulted in power ratings between
approximately 7 and 10 watts. This considerably reduced range was
closer to estimated realistic performance figures for the
solenoids. The solenoid experiments were carried out with
relatively conservative power supplies and it was speculated that
their performance may be improved through more efficient and
large power supply strategies.
The issue of power supply and usage was further complicated by
the differences between the mechanical operation of two hammer
systems - conventional and electro-mechanical. The hammers for
the electro-mechanical arrangement (discussed in the next
section) are heavier than the heaviest piano hammer by about 7
grams. The heaviest bass hammers on the conventional action are
approximately 13 grams while the iron solenoid cores alone
(without the actual hammer tip) weigh 20 grams each. However, a
larger hammer mass with less velocity could result in a similar
dynamic to a conventional lighter hammer travelling at a greater
velocity. This was not experimented with directly but was
recognised as an important factor in the performance of the new
In addition to the weight differences the operation of the two
mechanisms necessitates an alternate assessment of the mechanics
of the hammer movements.
An FFT plot of the hammer striking the lowest A on the grand piano.
The FFT plot shows that the time taken by the hammer
from initial impulse to string impact was approximately 18
milliseconds (ms) for the moderately loud case. From that time
onwards the hammer is returning to a rest position. The further
oscillations recorded on the plot are the movement of the hammer on
its wooden shank. For the initial thrust of the hammer the plot
does not show the point where it is free from the impulse of the
keystroke force and travelling without further propulsion.
Although this period of free flight may well be negligibly small,
by contrast the solenoid remains under power and acceleration
until it impacts on the string and potentially interferes with
It is expected that the solenoid can be powered up for an
approximately equivalent period of time as the normal hammer -
about 18ms. But that also depends on the intended dynamic. The
dynamic range for the electro-mechanical action is achieved by
turning the solenoid off at various stages after activation. The
loudest attack will result from the solenoid remaining powered up
fractionally beyond the time of impact. This may be 20ms while
the softest attack might only be a 6-7ms period. An influential
factor in the timbral quality of a struck string is the reflected
waves from the shortest end of the instrument which return in
approximately 9ms. The longer the solenoid remains in contact
with the string, the more the hammer interferes with the evolving
Construction of a New Action
The question of performance was momentarily put aside when time
came to consider construction of the action. After all, abstract
performance questions were of little consequence if it turned
out to be impossible or impractical to construct a mechanism -
using the resources at hand - that could fit into the complex
cavity that normally houses the conventional action.
Through the theoretical principles of operation and those
existing components that were inextricably part of the 'grand
design', some idea of its form was known in advance. However,
from February of 1988 to late June, many ideas and approaches
were examined and discarded as the search for a workable design
was given priority.
A scale drawing showing space restrictions inside the piano.
The action began to take shape in the hands of Marshall Maclean
in the Physics workshop at La Trobe University from June of 1988
onwards. Many of the technical and design problems that sprang
up during construction were resolved by him (see the working
sketches ). Without recourse to a piano at every critical point,
he produced an action that constantly met not only with
theoretical expectations but proved successful during
The action benefited from many important decisions made along the
way. Some of those were:
An examination of the photographs of the first (bass end) of the
three modular sections identifies the support structure for the
hammer and the damper solenoids. These are arranged in two
parallel rails mounted on adjustable feet. The hammer/damper
configuration met the functional specification of minimum moving
parts and autonomous control. The forward vertical rail is the
mounting for the hammer solenoids which are staggered in two
vertical rows. The rear shorter rail holds the damper solenoids
in a similar staggered configuration but this time back-to-back
on either side of the rail. The front rail has circular holes
drilled at intervals to allow the wiring that runs between the
solenoids and the driver boards to pass around any of the moving
parts and also reduces the weight of the system.
No specialised solenoids were to be constructed either for
the hammers or dampers. Those used in the Pianocorder mechanism
were considered to be suitable provided they could perform to an
acceptable level and be located in the already cramped space.
Development went ahead on those premises.
The action could be made to fit a number of instruments by
being modular and adjustable. The major obstacle, however, that
this attempted to overcome in the first instance was the intense
asymmetry and irregularity of the piano's construction. It could
not be assumed that internal structure, for example, would
remain constant or that it would change in a linear fashion.
Consequently, consideration was given to the possibility that
part of the action mount might cause interference with the
action frame, i.e. frame struts or sostenuto bar.
A preliminary test installation revealed that there was more
space available than initially thought. This meant that the
action could now reside well within the limits and permitted
greater variation between instruments.
Each of the three sections has at least one locating foot. For
the full action length there will be five: one at each end and
three located a various points in between. Since each module
locks together, two feet per module are unnecessary and only add
to the complexity of installation. Feet can be added or
subtracted during an installation depending on the particular
instrument. They are also locatable anywhere along the mounting
rail where the damper levers are absent. This will usually occur
when the frame struts separate the strings into sections.
The solenoid cores (the iron part which moves under the influence
of the magnetic field) will move 15 millimeters for hammer
operation and 5 - 7 millimeters to lift the dampers. The hammer
and damper movements are actually in contrary directions, that
is, the hammer solenoid cores move up while the damper solenoid
cores push down.
The dampers are operated in the same way as the original action.
The solenoid pushes down on a lever which raises the damper. It
is expected that these solenoids, while on for considerable
periods of time, will require less power. Consequently they will
not heat up so quickly nor be subject to aberrant
electro/mechanical behaviour such as core 'chatter'.
The action was not conceived as being a permanent part of any
particular piano. The full implications of this desire for
portability emerged as the research progressed and it was soon
realised that it was going to take a considerable amount of time
to assemble in an instrument. More over, it was going to be
tedious and frustrating due to the massive amount of adjustment
required to align damper levers and hammer solenoids. However, to
make the task easier, much of the adjustment and assembly was
envisaged as taking place before the action was installed. Every
attempt therefore will be made to alleviate complications with
the wiring and final adjustments before it enters the instrument.
A clearer understanding of solutions to these types of problems
are likely to result from installation experience rather than
A cross section of the action frame.
The action frame was machined from 16mm and 25mm aluminium plate.
This provides considerable rigidity and yet is relatively light
compared to the all up weight with the solenoids.
Testing and Performance Expectations
Once the mechanical component is completed the system will be
tested with existing electronic hardware to verify that it is
operationally successful. This testing stage will not initially
take place in an instrument since that adds unnecessary
complications. When the system has satisfactorily completed the
initial tests and been examined for any potential problems, it
will be installed within a piano and the testing will begin again
under the intended operational conditions.
Underlying the success of the project will be its ability to
perform to fundamental expectations. Since the movement of
each part of the action is very small, it should in theory at
least, function with considerable rapidity. This has been proven
to some extent on an earlier system (Riddell 1988). The
particular layout of the solenoids (vertically) introduces no new
forces other than the existing functional ones of
electro-magnetism and gravity. However, rapid operation may be
inhibited due to the sophistication of some of the co-ordinated
operations of the mechanism, where the dampers and hammers are
able to operate synchronously or autonomously during a
performance. In a normal operating mode, for example, a damper
should be free of the string by the time the hammer strikes. The
system is therefore required to have the damper solenoid
activated in time to avoid the hammer striking the string while
the damper is still relatively close.
Once the mechanical component has been tested, attention will
turn to the most critical aspect the system - real-time control.
An initial consideration of real-time operation results in the
view that a distributed approach may be necessary. That is, where
the management of complex scheduling and event structures is made
easier by partitioning and distributing computation and I/O to
subordinate processors. This simplifies and solves problems in
one area but unfortunately introduces problems in others.
Nevertheless, while control of one piano may not cause major
problems, a multiple instrument configuration would at least
increase the complexity of control by an order of magnitude for a
single microcomputer system and thus justify distributed
Irrespective of what approach is adopted, the system will remain
subject to change if circumstances warrant it. Consequently,
every effort is made to maintain flexibility throughout,
hopefully allowing change to one area without necessitating
extensive change in others.
Software is particularly suited to modularity and revision. If,
for example, the lower level processes manage the note by note
activity they need not change when software is changed at a
higher level. This is a common practice these days in software
development but difficult to carry out if the lower level
functions become to embedded or too specific.
From the outset of this project many obstacles and problems arose
that made it appear impossible. It was not simply the scope of
the project but the perceived inherent difficulties within each
major section. Months later when those obstacles can be
considered with some hindsight, it is clear that some apparently
insurmountable dilemmas were resolved with less effort than
initially imagined. Therefore to have even arrived at this point
in the project is very encouraging and although much work remains
to done, the next stages can be viewed less as a series of
problems to be faced and more as milestones to be passed.
1. The author gratefully acknowledges the financial assistance of the
Australia Council in this project.
2. I would like to thank Professor Keith Cole, Dr Ron Miller and
Horst Dressel of the Department of Physics at La Trobe University
for their co-operation and encouragement in getting this project
3. The action owes its existence to Dr Micheal Podlesak who
contributed his expertise and interest during the experimental
stage and Marshall Maclean of the Physics workshop, through whose
skill and insight the action takes its present form.
4. (see 3. above).
The Notation of Polyphonic Music. 900-1600.
Cambridge, Massachusetts: The Mediaeval Academy of America.
Publication No. 38. 1953.
Grover, David S.
The Piano. Its Story from Zither to
London: Robert Hale. 1976.
The Computer Controlled Piano: New
Performer, New instrument.
. Melbourne : NMA Publications 1982.
Riddell, Alistair. M.A. Thesis (in progress). Department of
Music. La Trobe University. Bundoora. Victoria. 1988
© 2001 NMA Publications and Alistair Riddell.
has worked on a range technology-related projects and created many works for
his own computer controlled piano action.
His more recent work includes numerous computer-generated pieces.
to NMA magazine index.