Musaico is now Universal on iOS. I haven’t yet tried this one but it does look like an interesting sketch pad. I think this App like a few others like it really rely on you prepping a few great samples in your own style to get the most out of them. Let me know if you have used this one. $3.99 USD.
“Musaico re-imagines the musician’s early creative process. Designed and optimized for the iPad, the interface enables artists to immediately capture ideas. Record, loop, layer, and remix sounds in real time, from layering guitar parts to looping rap beats. Pick it up and learn to make a quick sketch in a matter of minutes.” – musai.co
For more info: musai.co