Musical expression pedal

An expression pedal assembly for a musical instrument with conventional electromechanical control means of the pedal being replaced by proximity control means. The pedal assembly is comprised of a casing which houses a proximity detector plate, a proximity detector circuit and may include an audio circuit compartment. Earth shielding of the bottom and walls of the casing is provided. A heel rest at one end of the pedal casing serves to provide the only support for a musician's foot and is so positioned to support the sole of the foot above the proximity device to provide the musician with swift and fluent control of a musical function controlled by the response of the proximity device to movement of said sole.

This invention relates to electrical musical instruments, and more 
particularly to a foot-controlled expression pedal therefor. 
BACKGROUND AND SUMMARY OF THE INVENTION 
In many electrical, or electronic, musical instruments of today both hands 
of the musician are usually fully occupied in the creation of musical 
notes and in some instances the musician's foot is employed for obtaining, 
or control of, expression in the music. This is especially so in the case 
of the so-called keyboard instruments, and especially electronic organs, 
synthesizers and the like. The aim, for example, of an electronic organ is 
to closely simulate the sounds and timbre of many solo instruments which 
have totally different wave complexities, such as variable vibrato in the 
case of a violin and selective attack in the case of a piano. A form of 
synthesizer known as the "THEREMIN" has been proposed which utilizes a 
proximity detector device responsive to the capacitive effect of the 
player's hand in its region to create an audible tone changeable in pitch 
with hand movement to and from the detector. It is possible, by fluttering 
of the hand in space, to create a variable vibrato effect at the will of 
the player. Hence both the tone and its animation is determined solely by 
the spacing, and movement, of the hand from the proximity detector. This 
instrument is limited in the complexity of musical compositions capable of 
being rendered. 
It would obviously be a great advantage if an electronic organ could be 
equipped with the same manual control of animation of created sound, but 
as both hands are usually fully occupied in the selection of the tones of 
the musical piece, it is not feasible to incorporate the hand operated 
facility of the "THEREMIN". Furthermore, the desired effect cannot be 
created by merely utilizing a proximity detector device in lieu of the 
present-day electro-mechanical arrangement of the organ's expression 
pedal. The inertia and balance of the pedal plate and its linkage is such 
that sufficiently swift and fluent control is not possible with the foot 
satisfactorily to obtain the above effects and many others such as 
selective attack and accent on notes. 
A prime object of the invention is to provide an expression pedal for a 
musical instrument which is capable of improved control by the foot of the 
player than are contemporary pedals. 
In accordance with one general form of the invention there is provided a 
foot-controlled expression pedal for a musical instrument comprising a 
supporting frame, an electrical proximity responsive device fixed with 
respect to said frame, and foot support means on said frame engageable 
beneath the heel of said foot for the latter's only support and permitting 
pivoting of said foot about said support means for freely raising and 
lowering the sole of said foot above said proximity responsive device to 
change the response thereof. 
The invention will now be described in more detail with reference to the 
accompanying drawings in which:

DETAILED DESCRIPTION OF THE INVENTION 
The first preferred embodiment of the invention as shown in FIGS. 1 and 2 
consists of a rectangular box formed from aluminium box suite extrusion 4 
to provide a top, a bottom and opposite sides, and L-section extruded 
aluminium end pieces 5 and 6 are secured to the end portions of the 
extrusion 4 to enclose its open ends. An aperture 13 is made in the top of 
the box near the forward end. A relatively thin sheet of rigid 
electrically insulating material is applied to the top of the box and 
covers the aperture 13 and extends between the end pieces 5 and 6. The 
outside corner of the end piece 5 may be bevelled and serves as a heel 
rest pivot 8 to be explained hereafter. A rubber floor mat 9 may be 
attached to the underside of the bottom for frictional grip upon a floor. 
A transversely extending partition formed from L-section extruded aluminium 
divides the interior of the box into two compartments. A first compartment 
10 serves to house electrical circuitry associated with the pedal. A 
proximity detector device 11 is fixedly spaced from its detector plate 12 
which in turn is secured to the underside of the insulating sheet 7 in the 
aperture 13 of the second compartment of the box extrusion 4. 
The proximity detector device 11 may be of the capacity type detecting the 
capacitance to earth of an object within proximity range. Other forms of 
proximity detectors, however, may be utilized such as an inductive device 
(not shown). Such a device may control the illumination of an incandescent 
light bulb which in turn controls a light dependent device to which an 
audio circuit is responsive. This form of controlling means does have some 
inertia. An inductive proximity detector may, therefore, include a metal 
plate joined to a layer of organic insulative material beneath it, with a 
second metal plate positioned remotely above the first and having an 
organic insulative layer joined to the top of the second plate. The light 
bulb is connected to the two metal plates and the lower metal plate is 
connected to the secondary coil of an induction apparatus. In such an 
instance the top plate is the proximity sensor. 
It is not essential to provide separate compartments within the foot pedal 
box, but it will be found convenient for wiring of electrical acoustic 
circuitry in the compartment 10 to the proximity detector device 11. Where 
only a single compartment is provided and the acoustic circuitry located 
remotely from the pedal box, an earthed transmission cable may connect the 
latter to the device 11. 
It will be appreciated that an expression pedal constructed in this form is 
intended for portability and, therefore, the proximity detector device 11 
will be subjected to different influences depending upon surrounding 
objects and their materials. This change of influence can be compensated 
for by retuning of the circuitry associated with the proximity detector 
11. However, by this invention the compartment containing the device 11, 
whether it is the entire box or a portion thereof, is provided with an 
earth shield at least at its bottom and around its side walls. 
An important aspect of the expresson pedal casing described above is that 
the heel rest pivot 8 for the foot of the operator is a transversely 
extending surface, or line, to support the operator's heel 14 at or near 
its transverse centre line. It has been found that pivoting of the foot in 
this area enables the sole 15 to be moved swiftly and fluently by the 
operator. Not only is control by the operator of movement of the sole of 
his foot hindered by the contemporary practice of pivoting a mechanical 
expression plate near the centre of the foot, but these electromechanical 
pedal plates have considerable inertia. With the use of an expression 
pedal of the present construction, the control available to the operator 
of the movement of the sole of his foot with respect to the detector plate 
12 is such as to facilitate the creation of hitherto unobtainable musical 
effects, such as faster and more fluent expression, variable attack and 
accent on individual notes, and selective vibrato and tremolo animation in 
a musical piece. By the inclusion of a stop or tab upon the musical 
instrument the selective response of the detector device 11 may be 
switched from control of frequency for vibrato effects to amplitude for 
tremolo effects. As an alternative, the heel rest pivot 8 may be provided 
in the form of an upwardly projecting abutment against which the rear of 
the heel 14 may be rested for pivoting of the foot at this point. However, 
the control of movement of the sole 15 is not in this instance as 
pronounced as when pivoting occurs near the transverse centre line of the 
heel 14. 
The embodiment shown in FIG. 3 incorporates an electro-mechanical 
expression pedal combined with a proximity responsive expression pedal of 
the kind described above. In this case the mechanical pedal plate 16 has a 
conventional pivot lying beneath a central part of the operators foot and 
a heel abutment 17 is provided upon the plate 16 to allow the operator's 
foot to slide forward so that the sole of the foot overlies the proximity 
detector 11 and its detector plate 12. In this instance the box 4 housing 
the proximity device 11 is provided in open-topped form and is covered by 
the insulating sheet 7. The purpose of providing this thin sheet 7 of 
electrically insulating material, as in the instance of the embodiment of 
FIGS. 1 and 2, is to avoid contact clicks in the amplifier of the musical 
instrument when the player's foot is lowered onto the detector plate 12. A 
similar compartment 10 is provided for housing accoustic circuitry and a 
rubber floor mat 9 is also attached to the bottom of the unit. It will be 
observed that with an expression pedal formed in this way, a choice of 
either mechanical or proximity responsive expression control is available 
to the musician. When the mechanical pedal plate 16 is moved to its fully 
forward position, a foot resting upon it may be slid forward to the 
abutment 17 so that the sole of the foot lies above the proximity detector 
11. The detector 11 is earth shielded so as to be responsive only to the 
presence of overlying objects and is unaffected by a foot movable with the 
mechanical expression plate 16. 
In a further embodiment (not shown) a plurality of expression pedals such 
as described with FIGS. 1 and 2, above, may be juxtaposed for operation as 
selected by the musician. Each pedal, incorporating a proximity device 11, 
may be connected with the electrical circuitry for control of a different 
musical effect. In one application of this embodiment a single master 
oscillator may be used with each proximity detector device 11 controlling 
the operating frequency of a filter, with the amplitude of a high 
frequency signal at the output of each filter being detected to generate 
each control signal for controlling separate audio effect circuits. 
The musical expression pedal of this invention may be utilized in many 
different applications. For example, it may be applied to automatic bypass 
switching which can be triggered by a control signal derived from the 
proximity device 11 so that at the remotest proximity effect distance the 
bypass switch is switched on, while being normally off during response of 
the detector 11 to the presence of an operator's foot. Hence such 
switching may be utilized for bypassing the audio effect circuit 
controlled by the expression pedal. Furthermore, automatic bypassing may 
be switched in every alternate time the musician's foot is withdrawn from 
the pedal while alternately the audio effect circuit remains connected. A 
lamp indication may be used to record the state of the bypass switch. 
Also, automatic bypassing may be combined with sequencing of a number of 
audio effect circuits with indication of different effects by appropriate 
lamps. Therefore, when the musician's foot is withdrawn from the pedal, 
the automatic bypass may switch on and the next effect in a sequence is 
selected and will remain in circuit when the foot is placed back upon the 
pedal and can then be controlled according to the movement of the 
musician's foot. Upon the next removal of the foot from the pedal, the 
succeeding effect is selected. 
As further applications of this invention a combination pedal may be used 
to control flanging by the electro-mechanical pedal while double tracking 
or pure double tracking or pure differential double tracking is achieved 
by use of the proximity responsive device 11. For example, the expression 
pedal of the invention may contain a pure differential double tracking 
circuit with the duration control being controlled by the proximity 
detector 11. Automatic alternate bypassing may be incorporated so that 
while the musician's foot is removed from the pedal every alternate time, 
the difference between the time of arrival of the two audio tracks remains 
fixed at around say 1/15 of a second. In such a state the pedal produces a 
1/15 second double tracking effect without the musician's foot being 
placed upon the pedal. As the musician's foot is again placed on the pedal 
and the sole of the foot approaches the proximity detector 11, the time 
delay between the two tracks become less. As the sole of the foot attains 
the limit of responsive range closest to the detector plate 12 it may 
cause the time delay to diminish to around twenty milliseconds. An 
indicator lamp may be provided which is extinguished while the switching 
is in the audio bypassing state. 
Whereas several embodiments have been described in the foregoing passages 
it should be understood that other forms, modifications, and refinements 
are feasible within the scope of this invention.