This is music math nerdery. It started with Chris from Airwindows talking about how he discovered that certain tempos feel a certain way and that the feel repeats throughout different tempos in a cyclic fashion. Chris describes it much better than I can. So here a link his blog post:
Chris curve-fitted an algorithm for his findings, I noticed there were numbers that looked like π and made a version of the algorithm. Chris and I bounced this back and forth a couple of times and settled on a version of the algorithm. I liked its so much I decided to make a plugin out of it. Its quite simple to use. Pick a feel and find a tempo that suits your needs. You want decimals? You got it!
View the plugin as a guide. A sort of helper in that initial stage of songwriting. What could the tempo for this song be? Lets try “Swagger/Attitude” with “Parameter 12…!” How does 109.3 BPM feel?
Obviously. This doesnt apply to all music all the time. (Duh…) Theres the glorious examples of Stairway To Heaven and Bohemian Rhapsody plus a bunch of others. But a lot of classic pop hits fall in the range of this algorithmic Tempo Paradigm.
Maybe there is a way to dissect Stairway? Maybe the tempo feels that Chris listed aligns with the feel of the song. I havent checked. And even further than that – I havent checked the algorithm for where zero is. Maybe theres more to unearth. Time and further research will tell.