Review: Casio CZ for iPad

Phase distortion timbres never sounded so good
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Based on several conversations at this year’s NAMM show, Casio’s CZ for iPad has flown under the radar for quite a few iOS-based musicians. That’s a shame because it’s arguably an essential app for vintage-keyboard connoisseurs looking to have their favorite ’80s synths on hand.

The CZ for iPad combines classic Phase Distortion timbres from Casio’s ’80s-era CZ Series keyboards with modern features you’d expect in an iOS app.

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The app beautifully re-creates the sound of the original CZ Series hardware synths, such as the CZ-101, which relied on Casio’s innovative approach to digital synthesis called Phase Distortion (which some modern soft-synth developers refer to as “phase modulation”). Here’s a quick a recap of how the approach works.

Phase Distortion synthesis operates by distorting the phase angles of the sine and cosine waves that serve as the basis for the tone. Each oscillator starts as a sine wave, which can then gradually morph into one of 33 waveforms, determined by the configuration of its DCOs. For example, by selecting sawtooth as the target waveform, you can smoothly shift between sine and saw. What’s more, you can also select a second waveform to further shift the harmonic structure, with several options emulating the effects of resonant lowpass filters. It’s remarkable how intuitive this approach is, even after three decades, thanks to the iPad’s ability to display nearly all of these parameters in a single window.

The structure of a sound is straightforward, utilizing dual signal paths—called Lines—that consist of an oscillator and amp. There are three dedicated eight-stage envelopes per Line—one each for pitch, waveshaping, and amp—and the Lines can be arranged in one of three ways; single (Line 1 or 2), dual (1+2) or detuned (1+1).

There is also a single LFO dedicated to pitch that offers four waveshapes; sawtooth, ramp, square and triangle. (In my tests with version 1.1.1, I noticed an interface issue, with several of these waves not aligning with their label, but my ears figured things out quickly enough.) Additionally, there are resources for ring modulation, noise, and chorus/reverb effects, which add greatly to the synth’s tonal range.

Once you have a handle on the essentials, programming the CZ is a breeze. And learning to program this synth is crucial, as the app ships with a mere 33 presets that are decidedly vintage and, for some, nostalgic. Despite the synth’s digital pedigree, many of the patches veer into analog-ish territory, with brass sounds, woodwinds and classic leads dominating the collection (although there are some lovely bell-like textures mixed in for variety).

In addition to Audiobus and Inter-App audio compatibility—as well as an audio playback tool for soloing over your MP3 collection—the CZ for iPad app responds multimbrally over MIDI, with up to four patches available simultaneously. These can be mixed using a separate window, with chorus, reverb and a third selectable effect available via sends for each channel. In an interesting twist, CZ for iPad also allows you to set up multiple keyboards for playing each sound simultaneously, including a clever Mirrored mode that puts a keyboard on opposite sides of your iPad screen. Duets anyone?

All in all, Casio’s CZ for iPad is a fun trip down memory lane for anyone who was putting together their first synth rig in the mid-’80s. It’s easy to program, has a retro-digital sound all its own, and plays nicely with your other iOS apps. If you’re a fan of CZ-style Phase Distortion, it’s definitely worth the 20 bucks.

Perfect re-creation of Casio’s Phase Distortion synths. Four-way multi-timbral. Clean and intuitive interface. Integrated effects.

Slim selection of factory presets.


Producer Francis Prève has been designing synthesizer presets professionally since 2000. Check out his soundware company at