Sequle is musical scales based sequencing app. It uses musical scales theory to produce notes for MIDI-interface.

It has six tracks with note lengths, velocities and transpose. Tracks can have invidual pattern lengths and speeds. Song mode for more melodic performances. Minor and major scale and global transpose. It can be clocked either internally or from MIDI clock.

Using scales instead of specific notes makes everything sound good and it gives you more space to just play with the sounds get inspired easily.
Use note length and velocity to create rhytmical melodies. Vary pattern length to create polyrythmic sequences.

This app works with Camera Connection kit and most of the USB->MIDI converters.

The app is free to download but it has a limited playing time. You can purchase the full version with in-app purchase option and support the development.

Sequle is free on the app store, but the full version is an IAP away: