MIDI Pro provides practice opportunities and composition ideas.
The app allows you to selectively mix percussion and melody tracks so you can play along with your preferred instrument.
The generated MIDI sequences are a starting point for human composers to build upon and add more complex layers of instrumentation.
A mixture of determinism and randomness is used to construct MIDI sequences that can be tailored to individual preferences. 
The sequences are seeded with the selected rhythm, notes are are added using the selected key, scale and chord progression.  
The outcome is a set of tracks that include the percussion plus 4 melody tracks that can be individually adjusted.
With the paid version you can save midi files for reuse and or to import them into your favorite DAW.