I've had an idea in my head for a few years now - I'd like to build an electric trombone.
This is what I've got in mind:
The above does look a little ambitious, but perhaps I might get there in the third or fifteenth prototype...
My main question would be: what is the best sensor to use for the slide?
The slide has to glide smoothly like a knife through butter, and have as little momentum as possible - so you can do fast passages. The "rod" it moves up and down on should be as light as possible, otherwise there will be quite the moment when both handles are together (a counter balance might be needed... 
).
If you hold your left hand to your lips, and position you right hand as far away as possible, then that should be the maximum distance the sensor should have to sense.
If the above wasn't limiting enough, then the sensor should also have a good sample rate (in the milliseconds?), and a good sample depth (in the millimeters or fractions of a millimeter?).
From time to time, I've looked around for a suitable sensor, but I've never yet found one I've liked. The closest I've come accross would be to have a softpot with a wiper, or to use graycode on the slde - but I've never really felt satisfied with these solutions.
Does anybody know of any sensors that would be suitible for this?
Dave
Edit:
The MIDI specification for pitch wheels, is to use 16,384 possible variation values over 4 semi tones. The trombone slide covers 6 semitones (with 7 positions) over aproximately 600mm (about 100mm per semitone). So to use the same accuracy as a MIDI pitch wheel, the resolution would have to be 16384/4 = 4096 per 100mm, or 40.96 per millimeter. Obviously, this is a bit of overkill! I think the best sample deapth would be in the millimeters or fractions of a millimeter.
