MOTM

Hi Y'all!

Well, since this thread is still going, here's something else that's
sorta neat, though a one-trick pony:

Some time ago, I had a set of tuned steel bars (like glockenspiel or
celesta bars- mine came from a pipe organ 'harp' stop) which were
mounted over resonators. Obviously you could thwack them with something
relatively soft and get a sound like a vibraphone with the motors off,
or with something hard and get a glockenspiel 'tink'.

My dad and I had some electromagnets, basically iron cores with many,
many turns of wire around them, and we took a top octave generator
(50204), fed into a series of divide-by-two dividers, which then fed
what was basically a transistor pair-in-a-chip (ULN-2003?), which in
turn was connected to the electromagnet. You could select the
appropriate note, and drive the coil with a square wave-- holding it
over the center of the correct bar would cause the bar to vibrate at
it's fundamental pitch. Made an eerie sinewave voice which would
gradually build and then ring for a bit once the current was switched
off. 

We never made it into a keyboard instrument, but it was certainly an
interesting sound. Using frequencies other than a bar's fundamental
pitch tended to have little or no effect, though we didn't go to a lot
of trouble messing around with harmonics...

Fun though!

Frank Vanaman
Baltimore