In recent years, using iOS-based synthesizers onstage and in the studio has become a practical reality. One reason is that the latest iPads and iPhones contain more powerful processors than even some recent laptop computers. Apps are growing considerably more sophisticated and more closely resemble their computer-based equivalents, often by leveraging all that processing power. Thanks to economies of scale and the difficulty of pirating iOS apps, they’re also less expensive than computer-based soft synths and much, much less expensive (and often more versatile) than synthesizer hardware.
With dozens of synth apps available, you may want some guidance about which ones are worth your time and money. Although this list is by no means comprehensive, I recommend all 20 synths in this article for increasing your timbral range and musical creativity. All are polyphonic, all support Apple’s Core Audio, and all except for Roli Noise support Core MIDI and Audiobus. Some provide in-app purchases at extra cost to enhance or expand their capabilities, and additional presets are available for all of them.
The developer who created iVCS3 (iPad, $15) deserves heaps of credit for making such a faithful emulation of the classic, quirky EMS VCS 3, the first truly portable modular synthesizer. Launched in 1969, the VCS 3 had no hardwired connections; you connected circuits by inserting pins in a patch matrix. To connect a VCO to a VCF, for example, you inserted a pin at their intersection in the matrix. Although iVCS3 adds a keyboard and 16-step sequencer from later EMS instruments, it duplicates the original synth so precisely that I recommend reading the original VCS 3 manual if you want to master it.
iSEM (iPad, $10) re-creates the Oberheim SEM (Synthesizer Expansion Module), which was introduced in 1974 and supplied each voice in Oberheim’s legendary Two-Voice and Four-Voice models. Like the original, iSEM has two oscillators, a 2-pole multimode filter, and two 3-stage envelopes, and its warm, virtual analog sound might fool even a purist. Unlike the original, it also has a suboscillator, second LFO, arpeggiator, and 8-slot modulation matrix, as well as overdrive, chorus, and delay effects. You can offset the values of six parameters so that each of eight voices generates a different sound, making iSEM 8-part multitimbral, too.
Sunrizer (iPad, $10) is an analog-modeling synth with a distinctively digital personality. Resembling Roland’s JP-8000 in more ways than one, Sunrizer gives you two oscillators featuring stackable super-saw waveforms and two independent filters with a selection of 15 types. In addition, it offers numerous effects, an onboard audio recorder, MIDI CC mapping, up to 20 voices of polyphony, and an arpeggiator that lets you design your own patterns. Sunrizer is also available as an AU and VST plug-in ($50) for the Mac and Windows, and a scaled-down version called SunrizerXS ($3) is available for the iPhone.