analogue and digital FM. differences/ similarities

[oblioblioblio]

Fm is way cool.

I really think that Buchla had it nailed down for working with FM. 2 oscillators with sine and more complex waves, and abilities to affect those waveshapes, and with room for applying control signals to most parameters.

FM can be tonal or atonal. It's completely mathematical. You have 2 oscllations, and by applying one to the frequency of the other, you get a waveform that includes aspects of both. If you move the 'root' of each osc up and down you can preserve exactly the same relative tonal content. So yes, you can 'play' the sounds. and also move them around many octaves.

I usually got a bit snowed under by polyphonic FM synths with like 4 or more operators. Just use 2 monophonically and see what you can do.

Search for vids of Buchla 200 series, or Buchla music Easel. Beautiful tonal and atonal sounds.

[steevio]

I dont know the differences between analog fm and digital fm, I dont know a lot about fm full stop but Ive been meaning to get into it.

I like some of the sounds, esp those of a percussive nature and those that are of a inharmonic nature. Often though, due to not being aware of the frequencies and only hearing the resulting sound, I have rarely been able to sit them comfortably in any piece of music.

In essence, it seems reasonable to assume I could start with a fundamental frequency that relates to whatever bit of music Im doing and create inharmonics for bell-like timbres and ultimately be able to sit those in the track. Sort of like, inharmonicity, but with a fundamental that allows them to be played chromatically to some degree? (hmm, or is this additive synthesis?)

Like is it possible to start with related frequencies, say 2 partials or more and then incur more inharmonic tones higher up? Kind of creating 'chord like' tones that still have an essence of being related to note values at the fundamental level? Hard to describe but my fumbling about hasnt left me with the knowledge on how to get the kind of sounds im after. Had some whacky and interesting results but nothing that easily finds its way into music. But with all the recent talk of frequencies I have been thinking of a bit of a resurge into fm and applying a bit more math to see if I can get predictable sounds.

My only form of fm synthesis is fm8 at the moment though but its a start.

this is pretty much what ive been doing since i started making techno.
i work to a fundamental tone (whether its actually in the tune or not, it can be 'implied') but for techno it works really well if this tone is the kick, and all my percussion is made by starting with a sinewave which is a harmonic of that tone. sometimes for high percussion it can be quite a distant harmonic, and not related at all in a 12 tet way. the sinewave can then be waveshaped to create whatever type of percussion you want, hihats, congas.. whatever, but there will always be a mathematical relationship between all your percussion, and its not 12tet.
this can be layered above other lower parts which are 12 tet and still work, it doesnt have to be all or nothing.

[AK]

Great stuff, was gonna ask something but before I do, I think I might be getting confused.

Lets say I have a sound which has a fundamental at 40hz, now I was thinking that the harmonic series (based on the 40hz starting point/fundamental) that the harmonically related partials would be going up by a frequency of 40hz each time to infinity. Ok?

But then it just occured to me that im talking about a sawtooth waveform. (i could google this but my phone browsing is tedious)

So whats the math difference in the harmonic series and a sawtooth? (im assuming none)

[damagedgoods]

Great stuff, was gonna ask something but before I do, I think I might be getting confused.

Lets say I have a sound which has a fundamental at 40hz, now I was thinking that the harmonic series (based on the 40hz starting point/fundamental) that the harmonically related partials would be going up by a frequency of 40hz each time to infinity. Ok?

But then it just occured to me that im talking about a sawtooth waveform. (i could google this but my phone browsing is tedious)

So whats the math difference in the harmonic series and a sawtooth? (im assuming none)

The amplitude. The amplitude of each harmonic decreases as frequency increases. It's the relationship between frequency and amplitude of the harmonics (as well as that between frequency and phase) that gives each broadband waveform (saw, square, pulse etc) its characteristic sound.

[AK]

Youve misunderstood me, im on about fm synthesis, not the harmonic and amplitude properties of a waveform. Im fully aware of what that involves

[AK]

So in fm (modulation aside) any sound made up of mathematically related frequencies of the fundamental equals a harmonic sound. Ie: with a fundamental of say 40hz, anything that is a multiple of that like 80hz, 120hz etc, is going to produce harmonics and any deviation from this math relates to inharmonicity.

[steevio]

So in fm (modulation aside) any sound made up of mathematically related frequencies of the fundamental equals a harmonic sound. Ie: with a fundamental of say 40hz, anything that is a multiple of that like 80hz, 120hz etc, is going to produce harmonics and any deviation from this math relates to inharmonicity.

every multiple of the fundamental IS a harmonic by definition, and yes any deviation is inharmonicity.

[AK]

Yeah, Id had a few beers when I posted that original question and thought I was describing the harmonics math of a sawtooth, then I realised the math is the same for the harmonic series.

My favourite key is 'E' so Ive been geeking out working out related harmonics to 41hz, but then I saw a frequency chart which has that low 'E' note at 41.2531 etc (not exactly that number just saying its decimalised) which is correct?