Drumming with her hands on the wall - joining in with this worked very well, she was looking and waiting and there was good turn-taking going on. She also enjoyed having the little plastic teddy bears poured over her head and said 'teddy bear' at one point.
A funny incident occurred later when she was playing her drum. I thought it would be a good occasion to join in by mirroring her rhythms and establish a turn-taking sequence. M. had other ideas - it was clearly a solo event. After a few efforts on my part to get in there she glared at me and shouted 'spoiling it!'. I was so happy about that use of language, both functional and actually quite advanced.