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 Forum index » How-tos » Micro Tuning
Microtonal keyboard - finished at last
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Octahedra



Joined: Nov 29, 2008
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PostPosted: Sun Dec 12, 2010 8:07 am    Post subject: Microtonal keyboard - finished at last Reply with quote  Mark this post and the followings unread

Well I've finally got this microtonal keyboard built and working.

It's designed for an equal temperament of 31 notes per octave. The white keys are the notes A-G (but not quite the same as the white notes of the usual 12-equal temperament) Every white note has a flat (above left) and a sharp (below right) which are black. The silver keys are double sharps and flats, and there are fewer of those because some are enharmonic (there isn't a key where you would expect to find E##; you have to use the Gbb key to get that pitch). I put green dots on to show the meantone scale of 12 notes per octave (give or take a cent here and there).

It's supposed to be a sort of compromise between the Fokker organ and more recent designs by Erv Wilson and Aaron Hunt.

It's isomorphic - moving across the keyboard in the same distance & direction will always give you the same change in pitch. Although a lot of the benefit of that is lost by not having a big 2-dimensional field of keys like the Fokker organ or Sonome/Axis. You can also map other equal divisions of the octave onto this key layout - especially the ones that work with 7 white notes plus sharps & flats (eg. 17, 19 & 29). But with those other tunings it's no longer isomorphic. I haven't programmed any of the others into my Tuning Box yet...

The range is 4 octaves (126 keys). It puts out ordinary MIDI, so you need a microtonal synth, or the right tuning software/hardware to convert the signal. The 2 buttons on the back are for changing the output midi channel and note velocity (it isn't velocity sensitive, which is fine for me as I'm definitely on the organ rather than the piano side of things). The key action is very light and noisy (microswitches), so it's only good enough as a composing tool, not for performance. It's easy to hit extra keys by mistake and trigger unwanted notes, because they're so small and take so little pressure. I'm not really happy with the key action at the moment, but if I ever get time I might try to come up with a better mechanism. For now I'm just glad to have the damn thing working after over a year of it sitting in the cupboard waiting for me to find the time and ideas!

Thanks to Jordan Petkov & co. at Midi Gadgets Boutique for building me a midi encoder circuit with the extra channel & velocity buttons. Thanks also to my dad for the photography.

Gordon


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seraph
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PostPosted: Sun Dec 12, 2010 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Gordon,

congratulations Exclamation
You wrote:
It's easy to hit extra keys by mistake and trigger unwanted notes, because they're so small and take so little pressure

It would be nice to have a picture with your hands on the keyboard to figure out the key size.
I hope you come up with nice music playing it Very Happy

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Octahedra



Joined: Nov 29, 2008
Posts: 149
Location: Cheshire, UK
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PostPosted: Mon Dec 13, 2010 7:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Carlo - I'll be playing around with this keyboard for a while and I hope to get more confident about composing in 31et as a result!

seraph wrote:
It would be nice to have a picture with your hands on the keyboard to figure out the key size.


I'll have a go at getting a photo soon (my only camera is in my phone, but it should be good enough for this)... In the mean time, the keys are about 11mm wide, with a 3mm gap between each row. I tried to make the width of an octave the same as on a piano keyboard, but because of the available wood sizes and a mistake in my calculations it's ended up a few mm wider. I can only just cover an octave with one hand, if I'm careful.

I reckon if these keys were more strongly sprung it'd be easier to avoid pressing them by accident. But they're hinged at the back like conventional music keyboards - the further back you press them the less leverage you get, so more force is needed. If they'd been built like computer keys, where the whole thing moves downwards without rotating, you could have stronger springing and be able to play easily by hitting any part of the key. This is of course how keyboards like Opal and Axis are generally done, and I think even the Fokker organ is like this.

Maplin doesn't sell individual computer keys any more, but I'm sure I could get some from somewhere if I do find the time to build a better version of this keyboard...

Gordon
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bachus



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PostPosted: Mon Dec 13, 2010 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Congtratulations indeed!

The carefully radially sawn fir strips appear to be passive mechanical support elements. Is that correct?

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Octahedra



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PostPosted: Mon Dec 13, 2010 3:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

bachus wrote:
The carefully radially sawn fir strips appear to be passive mechanical support elements. Is that correct?


Exactly - I glued all the wooden components together into a single fixed structure. The strips aren't all that carefully sawn though! Smile I've got a mitre saw that makes it dead easy to cut through strip wood at certain preset angles. I made them a bit too long and glued them on like that. Then brought them all down to matching size & shape with a power sander. I got the sander especially for this job, but already had the mitre saw and spray-on cellulose lacquer from an earlier woodwork project - making board game pieces.

The switch contacts stick down between the strips, and everything is wired up underneath. I had to leave some slack for moving each switch into a position above the board where I could reach to solder it properly, so there's over 20 metres of cable in there! It's only superglue holding the switches on - you can actually break them off to do maintenance if you need to, and just reglue back in the same place.

Gordon
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bachus



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PostPosted: Mon Dec 13, 2010 4:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Octahedra wrote:
The strips aren't all that carefully sawn though! Smile


Looks good enough to me Smile Actually I was referring to the orientation of the dimensioning cuts relative to the concentric ring structure of the wood. From what I can see they are all ideal (maximally stable in terms of tangential/radial delta forces that distort wood) -- what one would expect to see for wood dimensioned for actual wood keys. Which is what initially caught my eye and raised the question. I'm a bit of a tinkerer and always curious as to the how and why others select and use their materials.

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Octahedra



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PostPosted: Tue Dec 14, 2010 11:18 am    Post subject: Reply with quote  Mark this post and the followings unread

seraph wrote:
It would be nice to have a picture with your hands on the keyboard to figure out the key size.


Here we go - this is me playing a C major chord with my left hand. Lots of fingers flying around and keys that respond to very little pressure. Keeping fingers out of the way is a problem I'm having on the harp too.

Gordon


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Octahedra



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PostPosted: Tue Dec 14, 2010 11:30 am    Post subject: Reply with quote  Mark this post and the followings unread

bachus wrote:
Actually I was referring to the orientation of the dimensioning cuts relative to the concentric ring structure of the wood. From what I can see they are all ideal (maximally stable in terms of tangential/radial delta forces that distort wood) -- what one would expect to see for wood dimensioned for actual wood keys.


I'm afraid I never thought about the ring direction. The wood was already planed to a better quality on two opposite sides, so I made sure one of the smoother sides was always on top . The wood colour varied a little bit, so I just tried to mix them up as randomly as possible.

Gordon
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Acoustic Interloper



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PostPosted: Tue Dec 14, 2010 11:54 am    Post subject:
Subject description: Virtual keyboard
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Nice keyboard! I envy physical design/construction skills.

Here's the one I have been working on lately to play something in Just Intonation for NYE. You can adapt it to use a different temperament/intonation by writing a couple of simple Python functions, would work fine for microtones. It generates all the necessary GUI-buttons-as-keys based on the scale you are using.

This outputs MIDI, so with a given pitch bend working correctly for only 1 note at a non in a non-equal-tempered scale, you have to use multiple channels to get polyphony in a given voice. The four crossbars x0..x3 chain attached channels so you can get chords. The important feature that just went in today, though, is live coding for each channel. The Code button pops up a text dialog that lets you enter stuff like this
Code:

def genfunc(s):
   import random
   def r(lower, upper):
      return random.randint(lower,upper)
   dur = 1.0
   de = 1
   s.p = 80
   s.o = -1
   while True:
      s.b2 = dur
      yield de
      if r(0,3) == 0:
         s.b3 = dur
         yield de
      s.b1 = dur
      yield de
      s.b0 = dur
      yield de

Turning it into a player piano for Delicate Monster's "Crater Dust" piece that I'll be playing. The line "s.b3 = dur" for example triggers the button labeled b3 (the dominant 7th in this case) for dur * tickRate; the yield statements essentially pause for de * tickRate before doing the next step, as the music continues to play. I actually play the piece by tweaking each MIDI channel's Live Code as it goes along, and also by messing with the target software synths hosted under Live. I'll post the code on the NYE thread after NYE.


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bachus



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PostPosted: Tue Dec 14, 2010 2:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Octahedra wrote:
seraph wrote:
It would be nice to have a picture with your hands on the keyboard to figure out the key size.


Here we go - this is me playing a C major chord with my left hand. Lots of fingers flying around and keys that respond to very little pressure. Keeping fingers out of the way is a problem I'm having on the harp too.

Gordon


Really, that is just way cool! Love to hear some of what you produce from it.

And if it requires tweeking or reworking ... even the best of professional "tinkerers" consider the first of anything a prototype.

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Antimon



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PostPosted: Wed Dec 15, 2010 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Beautiful piece of work. Congratulations! The sideways picture looks like it's something out of a sci-fi movie. I too would love to hear some sound.
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