"Phase Modulation" vs "Frequency Modulation" in simple terms?

[buing]

But if many FM synths does actually PM, why they call their synths "FM"?
I just curious.

[foosnark]

But if many FM synths does actually PM, why they call their synths "FM"?

John Chowning was at Stanford University when he discovered FM synthesis, presumably using real FM (thru-zero linear FM). (He was experimenting with vibrato as a psychoacoustic distance cue, if I remember right, and either accidentally or out of curiosity raised the vibrato rate to audio rate. He and some mathematicians figured out the rules for how the process generates additional sidebands, given various ratios and modulation depths.) Then Stanford licensed the technology to Yamaha.

Yamaha engineers realized they could implement it more efficiently in real time in cheap 80s hardware if they used phase modulation instead.

Inside each operator there's a rising sawtooth wave representing the phase (generated by integer addition), which then goes through a lookup table to be converted to a sine. If you add the output of another operator before doing the lookup (again, just integer addition), that's phase modulation. No need to mess with actual frequencies. (*)

But they chose to keep calling it frequency modulation, maybe because of the license or maybe they just liked the phrase better


(*) you can do this with analog circuits too! The Happy Nerding FM Aid works this way, even though it's just a waveshaper that converts a triangle or saw to a sine in the same way that analog VCOs do. The "modulator" is just a VCA so you can control its mix level. It winds up sounding quite a bit like two operators in a DX7, except that there's usually a bit of extra buzz since things aren't mathematically perfect.

[LeVzi]

while the car drives at constant speed, someone moves the street back and forth.

I've had trips where that happens !

[vurt]

So what is 'NeoFM'?

from what i remember, an incorrect term, based on the assumption that they were doing something no one had heard of and rejected as a method due to its inefficiency in practical use.

[AnX]

5 years later....

[vurt]

5 years later....

it's been a busy 5 years

[j wazza]

frequency modulation is pitch modulation, it can be achieved with speed modulation of a sample and its easier to understand as speed mod

phase mod is like modulating a delay instead, moving the sound back and forward in time rather than speeding it up and slowing it down

but they end up having the same effect a lot of the time eg with sine waves, not with waves with straight lines like square, with pm this makes the sound suddenly skip to a different point in time getting pops, with fm it just suddenly accelerates to a different speed but the waveform is still continuous

with the car example its like a car suddenly skipping 5m down the road with pm, compared to suddenly going from 30mph to 60 mph with fm

in not so simple terms - fm doesnt exist in computer world all that called fm is.....variations on phase modulation, or if you really in a mood you can find out that even in hardware synths it's the same thing... or if you really wanna beimpresive on party in knock that hotlooking femlae/male you can say that 'fm was a word used in a patent from yamaha to describe phase modulation'

fm does exist digitally