Curating by tempo instead of genre
Launch library · evergreen read

Building a playlist around shared tempo rather than genre can produce genuinely surprising, cohesive results, grouping songs together by roughly equivalent energy even when their instrumentation or overall style differs quite considerably from one track to the next within the same collection, a method that treats energy, not style, as the organising principle.
This particular method works especially well for functional playlists, ones built specifically for exercise or sustained focus, where consistent pace matters considerably more to the overall listening experience than any single stylistic thread that might otherwise connect the songs together thematically, where the body's own rhythm matters more than any particular genre label.
Tempo based curation also tends to encourage listeners toward genuinely unfamiliar genres, since songs that would ordinarily never appear together on a typical genre based list can end up sitting comfortably side by side once matched carefully according to their shared pace, a pleasant side effect of organising by feel rather than by category.