I would like to share how I learned to remember 楽. To me, it is a picture of a large taiko drum sitting on a wooden stand. (Taiko drums are played at festivals and bon dances, and are a lot of fun to listen to.) The kanji 白 (shiroi, white) at the top is the actual drum. The two sets of small stokes on either side are the sounds as they project out from the drum. The kanji 木 (ki; tree; wood) is the wooden stand that the taiko drums sits on.