ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
ChordIQ - Learn notes, chords, sight reading, perfect pitch and more.
nlog Synth - Professional Virtual Analogue Synthesizer ::: check nlogmusic at YouTube :::
Tonaly - Compose songs and practice scales
zMors Modular - Full featured modular synthesizer for iOS
Scale Heaven - Browse and play any scale/chord, chord progression.