Know Sound Design: Wavetable Design

November 18, 2016

This month and next, we will explore wavetable design using Xfer Records Serum’s sophisticated EDITING tools. To begin, we’ll emulate the character of the classic Casio CZ-101 and its unique approach to waveshaping.

Back in 1986, the CZ-101 became a huge hit among keyboardists, thanks to its combination of affordable digital synthesis and multitimbral operation. Priced around $500, its FM-like method for waveshaping, called Phase Distortion, allowed users to smoothly morph from a sine wave to one of eight selectable waveforms, including classics like sawtooth, square, and pulse.

Xfer Serum’s wavetable design tools make light work of this task. So to get you started on creating your own wavetables, we’ll go over the essentials of creating a sine-to-sawtooth morph in Serum.

Step 1. Starting with Serum’s Init preset, click on the pencil icon next to the default sawtooth to open the wavetable editor.

Step 2. The sawtooth wave appears in the first index. Clicking on the second index will copy the original sawtooth to that position.

Step 3. Re-select the first sawtooth index (3a), then, in the harmonic editor at the top of the window, raise the level of the first bin to 100% (3b). This will transform the first index to a single sine wave at the fundamental frequency (3c).

Step 4. To create a wavetable that morphs from sine to sawtooth, click on the Morph pull-down window and select Morph - Spectral. This will interpolate between the sine and sawtooth waveforms, allowing you to transition smoothly between the two, just like on the CZ-101.

Step 5. Returning to the front panel of Serum, the WT Pos (wavetable position) knob adjusts the morph and allows you to modulate the waveform with envelopes and LFOs.

ProTip. Because the CZ-101’s Phase Distortion method also imparted a lowpass-filter-like quality to the waveshaping, you can add authenticity to this emulation by modulating Serum’s frequency cutoff, as well. Experiment with creating additional wavetables with waveforms such as square and pulse, because next month we’ll be returning to Serum’s wavetable editor to emulate PPG-style wavetables, which is a more complex process.

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