Old-school FM bass sounds in dance tracks

August 21, 2014

Most people associate various dance genres with their overall beats per minute and drum stylings, but equally important is the sound of the bass. What would dubstep be with out its wub-wub bombast? Or electro with its massive sawtooth basses? Or hip-hop with its reliance on sub 60Hz sine waves and TR-808 kicks?

In the April 2014 issue, I covered the new trend of square wave basses that are cropping up in deep house and techno. Well, that bass sound now has an even newer offshoot, courtesy of FM synthesis. Like the square wave bass, this sound emphasizes the odd harmonics, but with the added punchiness of FM and the snappy exponential decays that are often associated with its sound. Best of all, you can also create this sound with more basic FM soft synths, like Reason's Thor, which includes an FM oscillator option.

Here’s how to do it in both Ableton Live and Propellerhead Reason.

Step 1


Since this bass sound shares many properties with a classic square wave—that is, it features prominent odd harmonics—it’s quite easy to create using only two operators: one modulator and one carrier. By setting the carrier to the first harmonic (1) and the modulator to the second harmonic (2), the overall spectrum of the resulting waveform has that distinctly “hollow” sound associated with squares.

Step 2


In FM synthesis, the level of the upper harmonics is determined by the amount of FM applied to the carrier. Higher output levels from the modulator makes the sound brighter. Lowering that level functions a little like a low-pass filter, reducing the high frequency content. Adjust this level to taste, depending on how bright you want the bass to be in your mix.

Step 3


Finally, to add impact to this sound, shorten the decay of the modulator’s envelope so that it's in the 150 to 600-millisecond range. Again, this is a matter of taste as longer decays allow more of the “square wave” aspect into the sound, whereas shorter decays give it a stronger transient punch.

Step 4 (for Reason users)


If you’re a Reason fan, you can create an almost identical effect by selecting the “FM Pair” oscillator in Thor and choosing a 2:1 modulator/carrier ratio. Then, use Thor’s Mod Envelope (via its modulation matrix) to control the FM amount parameter, adjusting its depth and envelope decay in accordance with steps 2 and 3.

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