I have this app on my IiPad, and use it to practice. Probably not as much as I should. it does make practice easy. The diatonic button accordion is very unique. I first learned to play it playing only with an out bellows. I am now taking a course to play with both the in an our buttons. I also intend to learn playing only using one row. the way it was originally designed. We have made various instructional materials ( books, DVD's ) on how to play it, with Shelia Lee of HAPI in Houston.
i got this app sometime ago and use it a lot to practice the scales and learn to play tunes
one good and cheap app for ipad and squeeze box learners