Jamix for iPhone
This is how the app is described:
Jamix is the funkiest mix creating app on the App Store. Jamix allows you to record your own sounds and assign
them to its quirky looking symbols.
With Jamix you can record layered mixes created from your own sounds. Jamix creates beat sequence buttons and a funky rake
feature which allows for some effects that are not available in any other app.
The app is currently free, so why not take a look?