jpl@nyit.UUCP (John Lewis) (10/05/85)
The relation underlying FM is (in the most basic form) cos(I*sin(m)) = sum J<n>(I)*cos(n*m) J<n> being a Bessel function fo order n. The significance of this is that one can generate an infinite Fourier series weighted by Bessel functions using only two oscillators, and the effective bandwidth (to a greater extent than its character) can be changed by changing the parameter I. I think the idea that FM sounds are quite good got started in the early days of computer music when it was one of the only affordable methods known. To my ears this idea is way off--Fm covers the range of electronic bell sounds, from doorbells to menacing underwater bells... quite suitable for spacey muzak, or the carefully crafted bleeps of some serious, modern composers. The popularity of the Dx synthesizers suggests otherwise, but it may have more to do with what you get for the money than the actual quality of the sound (and of course one doesn't have to count on the timbre as much if other instruments are available) zilla NYIT graphics lab
jeq@laidbak.UUCP (Jonathan E. Quist) (10/08/85)
In article <137@nyit.UUCP> jpl@nyit.UUCP (John Lewis) writes: >I think the idea that FM sounds are quite good got started in the >early days of computer music when it was one of the only affordable >methods known. To my ears this idea is way off--Fm covers the >range of electronic bell sounds, from doorbells to menacing underwater >bells... quite suitable for spacey muzak, or the carefully crafted >bleeps of some serious, modern composers. The popularity of the >Dx synthesizers suggests otherwise, but it may have more to do with >what you get for the money than the actual quality of the sound >(and of course one doesn't have to count on the timbre as >much if other instruments are available) Apparently you haven't been exposed to _good_ Fm sounds. True, with just 2 oscillators you can get a wide range of sounds, but with MANY interconnected oscillators (study the patch diagrams on the dx-7, for starters) you can create some fairly realistic sounds, if you are willing to work at it. Unfortunately, Yamaha didn't include a mechanism for adding random variation in pitch and amplitude, which would have greatly improved realism. Of course, even with these additions, the dx-7's are still limited. What do you want for the price? A composer friend of mine has worked extensively in sound design with the Yamahas. He has access to a TX-816 (something more than 8 dx-7's), 2 dx-7's, and many $$ worth of computers running the MIDI, yet he still wishes he had more. With that much, though, he gets some extremely rich sounds. I don't mean to put down the dx-7's, but the preprogrammed sounds have a tendency to be a bit hokey. Still, if you take one you like, and twiddle the knobs a bit, the results can be quite satisfying. Jonathan E. Quist ihnp4!laidbak!jeq