Tuning tables

This is a forward of a letter i sent directed to the developers of HardSID,a very low cost synth soundcard for computers.Some of the ideas about tuning tables might interest people here...

(forward)

I have previously suggested implementing a tuning table for the HardSid software.So,here are the specifications.

The tuning table controls how the signals from the sequencer or Midi In is converted to pitch control values for the Sid chips on the card.The default mode for this is(i suppose)the standard 128 note MIDI range in 12-tone equal temperament,or 12tet.

With a user defined tuning table,each of the 128 MIDI notes should be able to correspond to ANY pitch within the SID chip range,as specified by 2 8-bit values.

The basic layout of the tuning table would be in terms of four columns:

Midi note number(1-128)
Hertz pitch(logical)
Cents value pitch(1/1200 of an octave)
Hexadecimal SID control value(for reference)

However,setting any of these manually would be quite tricky.So there should be some kind of simplifying automation script included.There are at least two such that would be simple and very usable.

The first one is support for equal temperaments.A MIDI tuning table of say,17 notes per octave would be easily created by specifying the cents value of one step(70.6 in this case)and the base pitch-for example,C-midi note 60 being the same.Since the total pitch range available is narrowed in this case,MIDI notes above C-60 will be lower and notes below C-60 will be raised above their usual 12tet pitch.

(note on equal temperaments:The use of ETS should NOT be restricted to octave based temperaments.There are many tuning systems based on equal steps not a equal division of an octave,which can be simply specified with a cents value.)

The second"quick tuning method",octave based tunings.This is used for scales based on Just Intonation(rational intervals)and subsets of ETs.In this case,you would specify what pitches you want in the octave and then they are repeated through the full available range.

How should one control what tuning table is used?Some manufacturers(like Yamaha recently did with their VL-70m)bind a specified tuning _to a patch_,which is an unwise solution.Generally one will want to use one tuning table for a song,applying this to whatever old and new patches are used within it.

So the tuning table could be saved in some sort of permanent bank of 128 or more tables selectable via a MIDI command,or be specified in its entirely.Both are rather impractical(the first method requires a part to install a new entire bank setup to play music by others).This is the main problem that remains.

One unsatisfactory solution is to have 128 PRESET tuning tables.However,the best idea would be to have the tuning table saved as an individual file,ready to be(automatically)loaded with each song using a non standard tuning table.

If you have any questions,just reply.A true implementation of tuning tables would put the HardSid cards way ahead of other similar synthesizers in a progressive musical perspective.

Thanks for reading,

-=-=-=-=-=-=-
MATS �LJARE
http://www.angelfire.com/mo/oljare
_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.