Recording FM Synthesizers

Recording FM Synthesizers

It's not the technology's fault that FM was overused in the 80s -

and it deserves a second chance

by Craig Anderton

When FM synths came on the scene in the mid ’80s, their bright, digital sound stood in stark contrast to their analog ancestors. Analog recording still reigned, and the DX7’s clarity was a fine complement to the warmth of analog tape (maybe it’s not a coincidence that analog synths made a comeback as the crossfade into digital recording occurred).

If you’re getting back into FM, or re-discovering its joys for the first time, here are some tips on how to get the best recorded sound. Don’t have an FM synth? Maybe you do . . . we’ll also cover some popular soft synths that have enough FM capabilities to get you started.

SPACE: THE FINAL FRONTIER

FM synthesis was very popular in “new age” type recordings, often providing bell and Rhodes-type sounds in a track with acoustic guitar, percussion, etc. However, when recorded direct with instruments that had room ambience—even trace amounts—it sounded somehow “wrong” because its ambience didn’t match up. I like to insert four delay lines in the synth's audio track set to short, prime numbers (e.g., 17, 19, 23, and 29 ms) with no pre-delay to create a sense of room ambience, even if it’s going to feed “room” reverb through an aux bus. The emulated “room sound” helps the synth blend in better with acoustic tracks (or samples that were recorded with room ambience).

DISTORTION? SAY WHAT?

Want a really cutting “lead guitar” sound that will not just jump out of a track, but make guitar players green with envy? FM’s basic sound generator is the sine wave, which just happens to distort beautifully. This is because it has very few harmonics, so adding distortion doesn’t create the screeching highs that normally make listeners dive for their earplugs.

However, sine waves by themselves are b-o-r-i-n-g, so most FM synth patches (with the possible exception of lame flute programs) add more operators to produce a more complex, interesting sound. We don’t want that.

Fig. 1 shows a basic fun-with-distortion patch, using Native Instruments’ FM8.

Fig. 1: This extremely simple FM7 patch works very well in conjunction with subsequent distortion.

I stripped the FM8's Glassy E-Piano patch down to two operators, D and F (you could of course use any two operators). F is set to a frequency ratio of 1.0000, and D to 2.000. D’s output modulates operator F and also feeds the audio output (the latter is optional), but note that it uses an amplitude envelope to fade in . Both operators also receive a little LFO to simulate a guitar’s finger vibrato, controlled via mod wheel.

When you press a key, operator F supplies the fundamental. Then the “feedback” octave higher component from operator D fades in over time—tasty! The output then goes through the distortion plug-in of your choice; I favor multi-band distortion, as described in the article The Guitarist's Guide to Multiband Distortion.

FUN WITH PANNING

Many FM synths offer interesting panning options. For example, the FM8 can pan each operator output anywhere in the stereo field. Yamaha’s ancient TX81Z (still wonderful if you can find one used) can pan notes in the stereo field based on note value (e.g., lower notes show up on the left, and higher notes on the right), velocity, or LFO frequency. These options help create more interesting stereo imaging.

YOUR SECRET FM SYNTH

Want to experiment with FM? You may already have some soft synths with FM capabilities. Usually this involves dual-oscillator architectures, where the output of one oscillator (the modulator) modulates the other oscillator (the carrier). You generally listen to the carrier output, and control the modulator’s level via envelope, mod wheel, etc. to adjust the amount of the FM effect. Synths I’ve used that allow for at least some form of FM include Arturia Moog Modular V, and Cakewalk's z3ta+ (as well as Cakewalk PSYNE).

So what are you waiting for? Get ready for the FM synthesis revival!   -HC-

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 Craig Anderton is Editorial Director of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.