# Discrepancy in spectral distortion

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

Hi Phil,

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

Best
K

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

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

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

All the best,

Phil

1 Like