Operator : adjust oscillators frequency in semitone offsets

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EricP
Posts: 19
Joined: Fri Jul 08, 2005 7:21 pm
Location: Paris

Operator : adjust oscillators frequency in semitone offsets

Post by EricP » Fri Sep 09, 2005 8:09 pm

I was trying to build a sound that had 3 oscillators tuned in a chord, with different envelope for each oscillator (like tuned echos).

there's no direct way to tune each operator in semitones (like 0, +4, +7) - or I didn't find it. Instead you have to use fine tune, which is expressed in thousands of an octave.

So, how do you convert fine tune setting into semitone ? There must be a formula (using log ...) but I was too lazy to look for it.

Instead, I experimented and build a conversion table.

The way I built the table is the following:
- use 2 operators in parallel, with basic sine preset
- play both operators continuously with same note (like C3)
- transpose operator A by -1 semitone (global transpose param)
- adjust operator A osc A fine setting until the 2 operators are in tune (use beating to fine tune)
- record the value
- repeat with 2, 3, ..., 11 semitones

Here is the table :

semitone / fine
0 ----> 0
1 ----> 60
2 ----> 123
3 ----> 189
4 ----> 260
5 ----> 335
6 ----> 414
7 ----> 498
8 ----> 587
9 ----> 682
10 ----> 782
11 ----> 888
12 ----> 1000

If someone has more precise values or the formula, I'd appreciate the update.

EricP

hambone1
Posts: 5346
Joined: Fri Feb 04, 2005 8:31 pm
Location: Abu Dhabi

Post by hambone1 » Sat Sep 10, 2005 11:42 am

Eric... you need to get out more, dude...

Arrowhead
Posts: 9
Joined: Sun Jun 06, 2004 3:28 pm
Location: the Netherlands

Re: Operator : adjust oscillators frequency in semitone offs

Post by Arrowhead » Tue Sep 13, 2005 9:36 pm

Having almost forgotten how to do this, but with your experimental table to check my attempts against, I came up with the following perl program:

Code: Select all

my $m = 2**(1/12);

foreach my $s (0..12) {
    print int(0.5+1000*$m**$s-1000), "\n";
}
which gives

0
59
122
189
260
335
414
498
587
682
782
888
1000

EricP
Posts: 19
Joined: Fri Jul 08, 2005 7:21 pm
Location: Paris

Post by EricP » Thu Nov 24, 2005 12:52 pm

cool ;-) I'll implement the formula in xls until Ableton adds the semitone display

thanks
EricP

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