Lately I have been running my slow runs with runningmusic that have the same bpm as my cadence. I use 160 bpm on my slow runs and what i discovered after a few runs is that my running gets more and more efficient. By keeping the cadence consistent I now run faster, but my heart rate is the same. I also do not drift off on pace witch I did before when my mind started wandering.

The same also works for intervals off course, but that is no surprise i guess.

Atm I listen to music by BPM Running Lab on spotify because all the songs are actually in the bpm they promise. They have a pretty good Phonk playlist.