I think 8 is a good number too, but at the same time, for the example you gave of the development of the different periods of jazz I would want more. maybe between 8 and 12? 20 is a bit much. though, regarding development of the different periods of jazz, wold you want a playlist for each period, or an overview of all in 8-12 tracks?
I guess there shouldn't be a hard number, but striving to keep the tracks to a minimum is a good idea. Whatever is deemed necessary. 8-12 would be fine, with the overview in just those 8-12 tracks. I feel if one enjoys part of the playlist they would able to explore on their own, which is half the fun.
| I feel if one enjoys part of the playlist they would able to explore on their own, which is half the fun.| for sure. I definitely would want this to be a jumping off point for exploration, or even more specific playlists.