From MarketingProfs (registration may be required):
if consumers are listening to a mix of songs that are relatively similar (eg, all love songs from the same artist), they remember their experience as more positive when the songs are ordered from least- to most–liked. In other words, a positive memory is affected by whether the trend became more positive or negative. In contrast, if they are listening to a mix of songs that are quite different from one another (say, different artists), their memory for whether the experience was good or bad is affected purely by how much they liked only the last song played.
What this means is that it’s not just about the mix, it’s also about the sequence.
So, for example, shouldn’t you play the “best” song right before the break, since it’s not likely that you’ll program a progression from worst-to-best?
Wouldn’t you always want the last song folks hear to be the best song you can possibly play?