I made a nice FM synth using OSC~s.
Then I thought it would be interesting to use waveforms stored in arrays so that you could change the basic waveforms…. so I replaced the carrier OSC~ with a PHASOR~ multiplied by the length of the array, into a TABREAD4~.
I put a sine into my array.
Already it sounds completely different to using an OSC~, even though the contents of the array is just a sinewave.
The modulator waveform is still generated by an OSC~.

Any idea why it sounds so different?

Tabread4~ uses 4-point interpolation, so the first two values of the waveform have to be appended to the end and the last value has to be prepended to the beginning of the array. Kinda confusing, but maybe thats why the sound is different?

Thanks…. it turns out my array was a different size to what I thought, so I was reading a load of silence on the end of my waveform.
Sounds good now, but leads me to another question:
when you use a SINESUM message to create an array with a wave made up of sines, I thought the first number was the size of the array. but it's not, for example If I define an array "abc" with 5002 entries, and then use a message [SINESUM abc 5002 1} then I get my sinewave but my array is resized to 4099 entries long.

why?

Hello......and well spotted @nuromantix...........
There is quite a good (and understandable!) explanation here..........
http://forum.pdpatchrepo.info/topic/506/4-point-polynomial-interpolation-care-to-explain
David.