FM ratio in zebra ?

[PaulSC]

(This very thread has them in cents.)

[giorgiomartini]

hey urs , one question please

im learning fm synthesis this is what i understand:


A Carrier is modulated by a Modualtor , if the modulator is very low the sound is like a police siren
if the modulator goes higher than 30hz then the more harmonics are created and the pitch goes higher everytime.
so , if you use a ratio like 1:2 you get harmonic sidebands , because the freq of the modulator is the double.





My question is :

if my sound is on C3 and i modulate it with a modulator with the double of freq than my carrier (1:2 right?) ,
how much is that in tones ? C3 plus D3 , or one octave higher ?


thanx!

2:1 = one octave up (1200 cents)
3:1 = octave plus perfect fifth (~ 1902 cents)
4:1 = two octaves (2400 cents)
5:1 = two octaves plus major third (~ 2786 cents)
6:1 = two octaves plus perfect fifth (~ 3102 cents)
7:1 = two octaves plus harmonic seventh (~ 3369 cents)
etc.

if i mudulate a carrier with the same freq but some tones higher or lower, there is the posibility to get inharmonic sidebands ?

i mean if i have a C3 and i modulate it with a G3
or a C3 mudulated with a D#


this are harmonic chords , but would i get inharminic results if i use these as Carrier and modulator ?

and why does "3:1 = octave plus perfect fifth (~ 1902 cents)"
need those 2 extra cents ???

sorry for asking so much , but i want to learn

thanx!

[Urs]

i have a C3 and i modulate it with a G3

The G3 is only half an octave higher, so it's not a clean harmonic. The first clean harmonic is a *whole* octave higher.

The next harmonic would be 3 times the frequency, which is 2 cents above G4. Why? Because we use well tempered scale instead of pure scales. In a pure C Major scale, the G would be two cents higher than in the well tempered / equal spacing scale.

Cheers,

Urs

[groundhum]

there must be a table somewhere...

Yeah, isn't it in the excellent DX7 manual?

Or roll your own.

Or CCRMA for the math inclined.

Or even Wikipedia isn't too bad at explaining it.

[bwong]

great thanx!


what does even means ? do you know a sinonim ,

does it means integrers ?


thanx!


and also , how is that table called , i googled tones to ratio table but nothing comes up.

You are apparently trying to draw a simple one-to-one relationship between "tone" and CM ratio. The reality is not quite so simple.

For one thing, the "standard" tuning is 12-tone equal temperament, usually abbreviated as 12TET. Sorry to contradict Urs, who is just trying to help, but "well-temperament" is not quite the same thing. Well-tempered tunings make certain keys sound better at the cost of other keys sounding worse.

FM ratios are of direct multiplication of frequencies. Therefore a ratio of 1:2 is stating that the frequency of the modulator is one octave above that of the carrier. That octave above the "fundamental" is called the 2nd harmonic. Easy enough, right?

Now consider a ratio of 1:3. That is 3 times the frequency of the fundamental (3rd harmonic). Bring that down an octave by dividing by two, and we get a 3/2, which is the same as 1.5. This is a perfect fifth. The problem is that standard 12TET tuning does not have exactly a perfect fifth. It is off by about 2 cents (1.96 to be more precise). To learn more about this you need to study harmonic theory. Hint : search for "Just Intonation".

The other thing to remember with FM is that the amount of energy in the sidebands is determined by the modulation index (MI), which is the amplitude of the modulator. A higher MI will push more of the amplitude into higher sidebands, increasing perceived pitch regardless of the particular CM ratio. Bump up the MI high enough and you will have no perceived pitch, just noise. Drop it low enough and the small amount of modulation will barely affect the pitch at all.

Here are a couple of my recent FM pieces. Each uses different single operator FM synths I made in Csound.

http://www.kvraudio.com/forum/viewtopic.php?t=263894
http://www.kvraudio.com/forum/viewtopic.php?t=266003

[mcnoone]

Here are a couple of my recent FM pieces. Each uses different single operator FM synths I made in Csound.
http://www.kvraudio.com/forum/viewtopic.php?t=263894
http://www.kvraudio.com/forum/viewtopic.php?t=266003

Thanks for sharing that information.
Learn something new everyday.

[Dexrow synths]

Here are a couple of my recent FM pieces. Each uses different single operator FM synths I made in Csound.

http://www.kvraudio.com/forum/viewtopic.php?t=263894
http://www.kvraudio.com/forum/viewtopic.php?t=266003[/quote]

It wo[quote][/quote]It would be cool to see those exported as csd. I am currently playing around with an fm I found at the texas am page (for testing purposes)

[bwong]

It wo

It would be cool to see those exported as csd. I am currently playing around with an fm I found at the texas am page (for testing purposes)

If you like I would be glad to supply you with .csd versions of each piece, though they were written in blue so the .csd will not be fully indicative of how the synths were actually used. The primary synth in FMain Street is controlled via blue automation (using lines on a visual graph). FMILY is using a standard Csound score-controlled synth, but I actually composed it with Python and Pmask scripting.

Contact me via PM and let me know whether you would prefer .csd or .blue versions. Also I just finished a 7-oscillator PM synth with full modulation matrix you may be interested in checking out.