It is also sadly necessary if you want to have any nested logic. As smart playlists are either x AND y AND z or x OR y OR z. You cannot have X AND (Y OR Z) for example without having 2 smart playlists one which is (Y OR Z) and one which is in Playlist 1 AND X.

I don’t listen to music very much on my iPod, sticking with mostly podcasts and audiobooks. But in order to avoid listening to the same stuff, I have a set up which randomly select 20 songs with a heavy bias towards least played. The chain runs as follows:

Grab everything marked as music or in the manual playlist of music exceptions (i.e. songs downloaded as podcasts)
Grab my 1500 least recently played songs from that list
Grab the 300 random songs from that list
Grab the 100 least played songs in that list
Grab 20 songs randomly from that list.

And then I created a playlist folder and hid all of the playlists except the last one in it.

I use a combination of Smart Playlists to construct a constantly changing playlist of about 50 songs for my commute that:

- exclude any songs in my iTunes I never want to hear (eg, stuff I bought for my kids)
- ignore tracks that are really short, classical, spoken, podcasts, or have fewer than 2 stars
- present me with up to 5 unrated or unplayed tracks (so I can rate them)
- play me the 10 3-star songs I listened to least recently
- play me a mix of 4-star songs that I haven’t heard in ages and randomly selected ones I haven’t heard in the last week
- play me the 5-star songs I haven’t heard in ages
- play me the songs I’ve tagged “ATF” (all time favourites) in the Comments field I haven’t heard in ages
- play me the 5-6 songs I’ve manually put on my “High Rotation” playlist as songs I can currently listen to over and over.

Works a charm! My own personal radio station without Kyle Sandilands.