Medly - Tap & draw to create your song. No musical skills needed.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
Music Studio Lite - Music Studio Lite is an audio management application that provides easy-to-use commands for creating sounds clips with frequency, pitch, loops, rhythms, or others as an entertainment source.
AudioKit Synth One - Free & Open-source iPhone/iPad Synth 🎹
GarageBand - GarageBand is a fully equipped music creation studio for Mac
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.