of Microprocessors

MUSIC SYNTHESIS PRINCIPLES 35
ever, there have been gaps of many years, even decades, between when it
became possible to apply a technique and when it became practical to do so.
The Telehannonium
One of the earliest serious musical instruments that produced sound by
purely electrical means was conceived and built by Thaddius Cahill in 1903.
The device was called the Teleharmonium, and the name fairly accurately
described the principles involved. As with many synthesis developments, the
profit motive was the major driving force. Cahill's basic concept was to
generate music signals electrically and transmit them to subscriber's homes
over telephone lines for a fee. The signals would be reproduced by loudspeakers
for "the continuous entertainment ofall present." The "harmonium" part
of the name derives from the use of harmonically related sine' waves for the
synthesis of various timbres.
At the performer's end, the device resembled a conventional pipe organ
console with two piano-like keyboards and numerous stops for controlling
the timbre. Tone signals, however, were generated at kilowatt levels by
specially constructed multipole, multiarmature electric generators located in
the basement. Each generator had eight outputs representing a particular
note pitch at octave intervals for the 8-octave range. Such generators were
reasonably straightforward to build but were large, heavy, and expensive.
Although 12 were planned to cover all of the notes in an octave, only 8 were
actually built. The high power levels produced were needed to serve the large
number of subscribers expected and overcome transmission losses.
In addition to the generators, special multiwinding "mixing transformers"
were used to combine several tones together. A limited amount of
harmonic mixing was utilized to vary the timbre. This was possible without
additional windings on the generators, since the first six harmonics of. any
note on the equally tempered musical scale are also on the scale with very
little error. The amplitude levels of the tones were controlled by means of
inductors with movable cores to vary the inductance. In addition to the
tonnage of iron, miles of wire were used to connect keyboard contacts to the
other equipment. Overall, the machinery that was built weighed over 200
tons and required 30 railroad flatcars to move.
Generally, the device worked well and was adequately accurate and
stable. One problem that was eventually overcome was key click. Since the
tones were being continuously generated and merely switched on and off
with contacts, the attack of a note was instantaneous. If a key contact closed
at a time when the signal being switched was near a peak, a sharp rising
transient would be generated in the output line. The solution to the problem
was additional filter transformers to suppress the transients.
The other problems were mostly economic. Since the planned 12
generators were not available, some of the notes were missing, resulting in a