> Step by step

1. Understanding FM synthesis… for free!

1

Yamaha’s original DX7 was the synth that brought FM (or Frequency Modulation) synthesis to the masses. Only it didn’t really as it was far too complex to program, and only the likes of Brian Eno ever ‘got it’. Fortunately, it’s much easier to understand with one of our freeware stars, Dexed. First, initialise a sound at the bottom left of the UI.

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You’ll hear a very dull sine-wave type sound because this is the raw, initialised basic patch. FM synths use Operators to produce their core sounds and these use sine waves – hence the sound – but the idea is that Operators can modulate themselves and each other to produce complex waves, hence the name Frequency Modulation.

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This signal structure is called an algorithm and on Dexed you can see the algorithm in use in the bottom centre of the UI. Dexed comes with several premade algorithms that can be selected using the Algorithm dial at the top right of this section.

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Select Algorithm number 9. The grid shows the structure of the Operators, with the bottom two Operators – in this case numbers 1 and 3 – feeding to the output, while the ones above them are modulating them. Here, then, Operator 2 is modulating 1 and itself, while 4 and 5 are modulating 3, while 6 is modulating 5.

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To get some sonic action going between the Operators, edit each one individually. We’ll start by going up to Operator 2 and raising its level to 1 o’ clock and then the Coarse Tune knob to F=4. You’ll hear a slight variation in the sound. For more drama, you need to modulate the modulators! Now turn EG levels 2 and 3 down, and EG Rate 3 to 1 o’ clock.

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As Operator 2 is modulating Operator 1 (and itself) changing 1’s envelope should also yield results, so play with the dials on that, setting them as shown. The resulting sound is like a marimba – a very typical FM sound. You can see and hear this in action from the classic video on the DVD or filesilo.co.uk.