9. Synthesising an FM bass sound with FM-4
1 It’s time to make a bass sound using 8-Track’s FM-4, a four-operator FM synth. Load it on a new Instrument Track. In the centre matrix, modulators are represented across the top, and destinations are stacked vertically. By default, Osc 1 is being modulated by itself and Osc 2 – turn both down to 0 to start from scratch.
2 We only hear Osc 1’s pure sine wave. In the rightmost vertical mixer, only Osc 1 (red) is being sent to the output – turn up Osc 2 (yellow) too, and you’ll hear it play an octave higher. We can control each oscillator’s Ratio by adjusting the top number for each – reduce both Osc 1 and 2’s Ratio values down to 0.50.
3 Turn Osc 2’s output Mix level all the way down again to silence it. In the mod matrix, turn the amount by which Osc 1 is being modulated by Osc 2 up to 250 or so. The inaudible Osc 2 is now modulating the audible Osc 1. To give each note more length, head to the amplitude envelope (bottom) and increase AEG Release to 39.
4 This sounds a bit static, so let’s modulate the inaudible Osc 2’s level with a new envelope. We click on the top + and choose ADSR from a list of modulators. Below, our new envelope is an arrow which is used to choose its target. Click it, find the Mod arrow for Osc 2, and turn it fully clockwise.
5 Click the arrow again, and our envelope is assigned. Turn that same Mod knob all the way down. The envelope will now control it. Let’s click the envelope to open its editor. Reduce Sustain to 0, and increase the Release. Decay should be at about 50. Now we’ve got a much nicer, ‘donkier’ bass sound.
6 Let’s get Osc 3 in on the action, using the same techniques we used for Osc 2. However, this time, we’ll have Osc 3 modulate Osc 2 in the routing window. We’ll also set its Ratio to 1.00. We’ll add another ADSR to modulate its Mod level and tweak it to taste. The result is a lovely, 90s-style FM bass sound.