this space intentionally left blank

January 2, 2008

Filed under: music»tools»synth

How to Create an FM Piano for Your Alesis Micron

I decided that I really do need to get serious about improving my keyboard skills, which have not been helped by the fact that my only instruments were either a 25-key USB keyboard (cramped) or a Yamaha DX27 (no velocity sensing, hard to program, the size of a small Volkswagon). So I used some of my Christmas money to buy an Alesis Micron, which is a virtual analog synth with 37 keys.

"Virtual analog," of course, translates to "can sound like a Moog Mini and a bunch of other synthesizers from the 70's." It doesn't do samples, and it doesn't do physical modeling. Those things don't bother me terribly much. It's still a really cool little box--eventually I will learn to use the built-in drum machine/pattern sequencer, and I will be crowned DANCE MUSIC KING OF ARLINGTON.

Conspicuously absent from the prodigious list of included patches, however, is a decent piano. Granted, classic analog synths were also notoriously bad at simulating acoustic piano, and the Micron does aim to mimic them. But it also includes basic FM capabilities for its three oscillators. As this video shows, they're more than capable of pulling of a piano imitation at least as good as my aging, 4-operator DX27, even while the patch creator is needlessly cryptic about how he put it together.

Well, I feel no need to be cryptic, and I'm annoyed by the fact that there seems to be relatively little information out there for Micron programming, short of a Yahoo! group that I don't particularly want to join. So after poking around in FM synthesis research, pulling the presets out of the Yamaha, and fiddling with oscillator tunings for about a day, here are my piano patch settings.

Obviously the voice is polyphonic with no portamento or analog drift. The important parts of the voice are that it needs a small FM amount (2.8%) and an FM type (lin 2+3). I left all three oscillators as sine waves (as far as I know, the DX synths only used sine waves for their operators), but oscillators 1 and 2 are shifted down one octave. Oscillator 3 is shifted up one octave and seven semitones. To remove some of the harshness from this sound, I add the Oberheim filter (ob 2pole) set at 1.307kHz with no resonance, keytracking, or offset.

Now we need to set the envelopes for the amplitude and the FM modulation. The former sounds natural to me with an attack of 1.99ms, decay of .5ms, sustain time of 1.816s, sustain level of 75%, and a release time of 214.7ms. I also send 75% of the velocity scaling to the envelope, to give the playing some dynamics. For the pitch/modulation envelop (Env 3), I use a .5ms attack, 96.6ms decay, 835.4ms sustain at 100%, and a 2ms release time. Looking at my settings, I'm not actually sure that this envelope is being used, but I'm including it here just in case.

The only thing left that's important is the modulation matrix. Envelope 3 is sent to the FM amount, with no offset or level (guess it really isn't doing anything, but setting level to .7% can add a little edge). I send M1 to the FM amount, which is useful for turning the piano into a harpsichord, and M2 is used to add reverb through FX1 (I prefer just a little bit of plate 'verb). By setting the x, y, and z knobs to control FM type, Osc 3 octave, and Osc 3 semitone transposition, you can experiment with the "tone" of the piano, making it harder or more bell-like to taste.

It's not as realistic as a sample-based piano, but it's a classic FM piano sound, and it will do for stage purposes. It also illustrates, I think, just how versatile the Micron actually is. I've only had it a couple of days, but so far I think it's a very impressive little box, and great for portable practice sessions.

Future - Present - Past