A couple of apps my buddy introduced me to. Great for travelling or composing
Thumbjam amazing app with a variety of instruments check out YouTube
Demos and the App Store . Apparently Jordan Rudess loves it
The next one was ifretless I hear the bass player screaming already lol.
I play bass and love it, the on screen strings are velocity touch sensitive
And vibrato too. There's a variety of bass instruments Jazz Bass,
Pick Bass, Double Bass, Yep Fretless Bass ,Bass Synth.
Great for backing tracks effects and a variety of sounds.
Again check demos and App Store