Lots of good advice in this thread (I'm new to concertina but coming to it from fiddle and I've given much of the same advice to students). I'll agree that it is worth investing time in playing by ear - it helps so much in getting the music to flow through you onto the instrument rather than coming off the page. As a fellow Mainer, I wanted to also recommend Maine Fiddle Camp - the second June weekend session always has concertina as one of the many instruments offered (both Anglo and English classes). There are sessions with a mix of instruments, including a slow session Saturday night. https://www.mainefiddlecamp.org/june-weekend-ii/
