AudioKit Synth One was a minor breakthrough for mobile music making as a free, open source synthesizer that could compete with the heavyweights, but its iPad-only nature limited its audience. You'll be glad to hear, then, that AudioKit Pro has launched a universal version of the app that works with iPhones. It's the same professional-grade hybrid analog/FM poly synth as before, complete with LFOs, oscillators, sequencers and hundreds of presets. It's just crammed into a smaller screen area. You wouldn't want to use this for full-time music creation due to the limited room for controls, but this could be helpful for starting work on a track when you're nowhere near a studio.