Forums > MaxMSP

transratio question

November 13, 2008 | 4:40 am

Hello friends,

In many example patches, like the transposition playground, I see a
sub-patcher called "transratio".

It is an expr with the following formula… ((440. * exp(.057762265 *
$f1))* 0.002273) that serves the purpose of turning pitch changes into
transposition multipliers.

The issue is that multiplying by 0.002273 is the same as dividing by
440. so you end up multiplying and then dividing by 440.

In the phase vocoder example by Dudas and Cort on the c74 site, this
same patcher is used, but its even more explicit:
expr ((440. * exp(.057762265 * $f1))/ 440.)

Now, Les and Richard are two gentlemen that history tells me don’t do
things for no reason. However, I can’t figure out why on earth this
formula multiplies and then divides by 440. Taking those two
statements out seems to yield the same results.

Any help anyone?

barry threw
Media Art and Technology

San Francisco, CA
Work: 857-544-3967
Email: bthrew (at) gmail (dot) com
Web: http://www.barrythrew.com


November 13, 2008 | 6:20 am

multiplication is less expensive computing, than multiplication. it’s mentioned somewhere in the tutorials.
jrp


November 13, 2008 | 7:31 am

While true, you are missing the forrest. When you multiply and then
divide by the same thing it cancels out.

I’m tending to think its just a "typo", but it’s strange to me that it
appeared in two separate patches…I’m just making sure I’m not crazy.

bt

On Nov 12, 2008, at 10:20 PM, jayrope wrote:

> it seems, that multiplication is less expensive computing, than
> multiplication. it’s mentioned somewhere in the tutorials.
> jrp
> –
> —
> fiction-induced heat
> on too many websites to name

barry threw
Media Art and Technology

San Francisco, CA
Work: 857-544-3967
Email: bthrew (at) gmail (dot) com
Web: http://www.barrythrew.com


November 13, 2008 | 8:00 am

Man, how i miss the forrest, spending way too much time in the city centre.


November 13, 2008 | 1:17 pm

The self-canceling 440.0*0.002273 is removed in Max 5.

< & Xoaz are great Max developers, but even the best of us does something unnecessary once in a while. The technical Latin term is "poopus cranialus"



kjg
November 13, 2008 | 2:06 pm

The only reason to use this number in a pitch related formula would be as the "A=440" (or 436, or 442 etc) reference pitch, right?

I use this for calculating transposition ratios.
[expr pow(2,($f1/12))]

the 12 can be replaced with another number for different equal temperaments.

regards,
kjg


November 14, 2008 | 12:01 pm

barry threw schrieb:
> Taking those two statements
> out seems to yield the same results.

I have done that as well, and it works. Simplifying the world never
hurts. No problem for me, and never expect the gurus to find always the
shortest path. They do mostly though and that’s fine…

Stefan


Stefan Tiedje————x——-
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