Re: MIDI key transducers (physical)
Re: MIDI key transducers (physical)
- Subject: Re: MIDI key transducers (physical)
- From: Ian Kemmish <email@hidden>
- Date: Tue, 25 Sep 2007 16:55:44 +0100
On 25 Sep 2007, at 8:26 am, Roland Silver <email@hidden> wrote:
I want to build a MIDI-like keyboard for playing scales based on
quarter-tones, i.e. for a 24-tone equal-tempered octave, rather than
a 12-tone octave.
Where can I buy the basic transducer that sits under each key? Not an
on/off switch, but one that transduces position (or velocity).
Actually, if you want quarter-tone, you probably don't want anything
like MIDI:-)
CoreAudio's StartNote() API allows you to have a fractional note-
number. This allows you have organs with split notes like Handel's
(handy for meantone tuning schemes), quarter tone keyboards or even
generalised keyboards (there's a nice diagram of the latter at
Wikpedia - without sacrificing the full ten-and-a-bit octave range.
Unfortunately host and synth support for StartNote() is patchy. My
synth supports it (and lets you specify tuning schemes with arbitrary
numbers of notes per octave, www.fdsynthesis.com), but at the moment
I'm not aware of any host software that supports it, and at one point
I even saw an Apple employee here threatening that it might one day
be withdrawn:-( I'm working on the principle that the more people
speak up about the need for this, the safer it's likely to be...
Well, that's the anti-MIDI rant over. Now for the mechanical bit:
In the days when there used to be a point to building homebrew
electronic musical instruments, the usual solution for touch
sensitivity was to have two parallel rails running along beneath the
keys. The key actuator moved a phosphor bronze wire (one for each
key) between the two. Logic would scan all the keys at high rate and
count the time it took for the wire to move between the two rails.
Maplin Electronics supplied the parts here in the UK and I made one
(not touch sensitive) using their parts around 1980. Electronics
Today International published various designs for pianos and synths,
explaining what the electronics had to do.
Wendy Carlos also describes a homebrew aftertouch mechanism based on
(as far as I can tell) strain gauge technology. Her website has info
on how to mail her if you want to ask her about this.
There also used to be at least one company that made MIDI retro-fit
kits for normal pianos, that you fitted on the keybed under the
keys. You might be able to cannibalise one of those. The company
concerned might have been Gulbransen, but I'm not sure about that.
Maybe your favourite search engine can help:-)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - -
Ian Kemmish 18 Durham Close, Biggleswade, Beds
SG18 8HZ
email@hidden Tel: +44 1767 601361 Mob: +44 7952
854387
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - -
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden