What works for me is to have a pool of thousands of “songs I like” - but then you’ve got the mood problem: Metallica or Sarah McLaughlin? That’s what AcousticBrainz was good at: picking through my collection for similar songs and playing that “mood” from the pool of songs I’ve already indicated I like by including them in the available list to choose from.

Where it excelled was at finding the outliers, like the relatively quiet Metallica song that fits with the current set.