The Mellotron is essentially a keyboard where each key
controls the playback of a prerecorded sound. Originally,
there would be a series of magnetic tapes, each with a
single note recorded upon it. Pleasingly, you could
replace
the whole bank of tapes to obtain alternative sounds...
Perhaps
you regretted your original choice*.
It occurs to me, that the difference between notes is just
a
change in frequency. Instead of having many tapes, why
not fewer tapes and a mechanism of changing the speed?
Now, you could just power the tape with an electric
motor
and speed/slow the motor based upon key input. This
would work, but, there might be some spin-up/spin-
down
time. You may go from A# to F through a bunch of out-
of-
key notes, which would sound bad.
How about a little F1 technology? F1 cars have multi-
clutch
transmissions which can swap gears in the single-digit
millisecond range. That's fast, fast enough that you
wouldn't really hear it. How about setting up the
keyboard
as the control panel for a 35-speed gearbox? With the
tape
drive being the output. Chords wouldn't really be
possible,
but that hasn't harmed the career of the recorder. Bonus
points if the power source is an F1 engine.
Inspired by <link>
* Restraint is advised when selecting the first tape set,
"injured cat" may have initial appeal, but no one wants a
recital interrupted by the militant wing of the RSPCA