(which I have organised by artist, and hence have 40-50 top-level items)

A somewhat inelegant way of handling this is to take your top-level items and subdivide it, i.e., "Artists A-E"; "Artists F-J", "Artists "K-O", etc. This will reduce the number of keypresses to drill down to where you want to be, but adds complexity to the overall playlist.

On my player, I can't get to a song without going through "Playlists", "Classical", "Composers A-G", "[composer name]", "[album name]", and then finally "[song title]". It's a bit cumbersome, but it is fast.

tanstaafl.