Discrepancy in spectral distortion

[psingleton]

Hi,

This is probably a very simple issue to resolve, but I’d be grateful if someone were willing to point out where I’m going wrong.

I’m still basically a beginner in using OM, but I’m using it to derive distorted spectra for an orchestral piece on which I’m working.

When I generate a spectrum with fundamental 55Hz (so A1), distorted as shown (fx^1.25):

the result is as follows:

When, however, I calculate the frequencies manually, I obtain a different set of pitches - for example, the 5th partial (55 x 5^1.25) has a frequency of 411.22Hz, which is close to a G# (415.3Hz), rather than the E natural that OM gives.

I’m deliberately using semitone approximation due to the forces for which this is intended, and I realise that approximating to 1/4, 1/8 etc. would refine this further - but that wouldn’t solve this wide discrepancy.

I’m sure there’s a perfectly rational explanation - as I say, I’d be very grateful if somebody would set me straight.

I’m planning on signing up for the Introduction to OpenMusic course very soon…!

All the best,

Phil

[haddad]

Hi Phil,

Please do send patches also. this will help for a fast answer.

Best
K

[haddad]

Dear Phil,

Here is the correct “patching”:

the error is to use an arithmetical series, whereas you are looking for an exponential factor.

Here is the patch:
Patch 2.omp (7.7 KB)

Best
K

[psingleton]

1.omp (4.4 KB)

I hope this will help… Between posting my question and this reply I’ve upgraded to the latest version of OpenMusic, which gives the same results.

Many thanks for having a look.

All the best,

Phil

[psingleton]

That makes perfect sense - thank you so much for the fast reply.

All the best,

Phil