Nanostudio 2 for iOS and the sound IAPs are now free, dunno if it's permanent or a temporary giveaway:

https://apps.apple.com/us/app/nanostudio-2/id1112601015

A very solid sequencer for all kinds of electronic music, has a solid synth/sampler and a drum sampler built in, and basic FX. The piano roll MIDI editing is very intuitive and one of the best ever made for a touch screen. Does MIDI synchronization and Ableton Sync too.

It's missing audio tracks (but you can record into the sampler if you wish), but otherwise an excellent tool. Just sprinkle some AUv3s into the mix and it's all good. For the record: I paid for the first one, and this one too, and it has been certainly worth the money.

 

I bought it some years ago and I liked it although I didn't write anything with it.
This app suffered from a lack of regular updates. Nothing like regular updates to refresh interest from customers.
Maybe it announces version 3? (with mpe and so on...)