They probably can't play slowly. I used to find I could play something fast, then when I tried playing it slowly it fell to pieces. I learnt to recognise that as a danger sign, and the cure was to practice even slower still until I could play it perfectly, and only then try it faster, and then it was much better (more even and rhythmical) that it had ever been.

Isn't the idea of a slow session for learning tunes? Mary and I ran a tunes workshop recently a bit like that. Very simple format - about 5 tunes, see how much a group of people could learn in half an hour. All we did was play each slowly and repetitively (lots of A's then lots of B's) and then put the tune together, then the same with the other tune, then the whole set. Simple but it worked well.

Anahata