[sdiy] Pressure + position based vibrato

[Edward King]

Hi guys. Sorry i havent contributed in a while, but a new client has me run 
ragged!

just before I left home to travel to the uk again, I was able to spend an 
hour or two on my aftertouch experiments.

Essentially, I was determined to try out all of the possibilities I listed 
as part of my journey through expressive capabilities. A number of 
instruments (including guitar and violin) were under-represented in most of 
the ideas I had and I havent had a huge amount of success mounting stuff to 
the tops of keys (even very low profile stuff dramatically changes the 
playability of the keys).

Consequently, I came to the conclusion that using a hard rubber bush 
mounting for a key on the pivot rod may give a key enough rocking movement 
to provide a differential from the key resting against either of two 
pressure sensitive pads (QTC material).

The initial experiment (although very rapidly thrown together) showed that 
even with rapid movements, there is enough of a difference in the outputs 
from the pressure pads to be readily measureable through ADC.

Questions arise (lifetime of rubber bushes, degredation, feel of the 
keyboard with all of the keys mounted this way - Ive only tried one so far 
etc) and Im sure that someone will have tried this before (very few things 
havent been tried have they?!) so I cant help wondering why it didnt work 
out (if indeed it did not).

The only other real issue is that now double the number of pressure 
sensitive pads are required (2 per key) but that these can double up as 
aftertouch when not used for the above purpose. Even so, more wiring, more 
complicated PCBs and more pics are required, which may put most people off.

Still havent ironed out the difficulties with my slotted optical switch 
based displacement sensing. getting close, but they're still unreliable...


EK