Yamaha DX21

1985, 8 note polyphonic, 4 operator, digital FM synthesizer

Yamaha DX21

I’ve had the DX21 for many years but never really taken the FM synthesis seriously until now, with doing some other video tutorials on synthesis I thought it was time to try again, also noting the DX7 is the same where I only knew the basics of how to shape a sound but no real understanding of how the FM synthesis works. After a bit of practice I’m now progressing really well with figuring out the subtractive frequency modulation and how to use it to create the timbre and harmonics you desire, having it running through the oscilloscope makes an enormous difference to understanding what you’re doing. I’d say the DX-21 is a brilliant way to learn basic sine wave FM without the additional complexity of the DX7, and I’ve already created some sounds and effects that show the real potential of this wonderful instrument.

Online you get a range of different opinions, but the one phrase which sticks in my mind is “thin and brittle”, and I can understand that comment given a flick through the factory presets, and a brief look at an initialised patch and what can be done with basic 4 operator FM. However, there are a couple of important parameters for getting away from the typical DX sounds, and I took up the challenge of making my DX sound fat! The DX21 has a feature which is unique to this model and even leaves the DX7 wishing it had the same: Dual Detune 99! Layering two copies of the same patch; with a variable detuning range of up to 99 (aprox 1/4 semitone)! Normal operator detune on the DX21 is only -3 to +3 (-7 to +7 on the DX7) which is not enough to make fat detuned sounds on its own. The DX7 does have dual-detune but the range is only 9 which means the DX21 is capable of much fatter sounds! Also both DX’s have a nice built-in chorus, and operator feedback which can create phasing or PWM style sounds.

Dual detune fatness: Make a basic square wave type sound and save it once to the A bank, and again into the B bank. Go into dual mode and load those two patches as your A & B, adjust the A/B Balance to hear one or both patches, with the balance in the middle; adjust the dual detune rate to make the pitch difference wider or more narrow. Now you hear analog style fatness coming from your thin and brittle FM synth ; )

Help! How the hell do you get lower case characters in the Voice Name?!

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