The role of the bass varies on the music, of course. New Order made the bass a melodic, lead instrument and the drum machine and synths the ‘new’ bass instrument; a lot of the Beatles’ stuff with those slinky Paul basslines he’s known for also works as kind of a lead guitar. A lot of funk or fusion stuff mutates the bass into something else like a drum (e.g. Primus) or a staccatto guitar (Victor Wooten with Bela Fleck, for ex). But for the most part, the bass functions as the center of a piece, tonally and emotionally. It becomes the simplest abstraction to a piece, implying chords and melody (when not explicitly stating both — Jaco was good at that, but his jazz sensibility meant that the songs weren’t ‘pop’, I think this is the crucial je ne sais quois that McCartney’s basslines really brought to the Beatles’ songs — his basslines were melody, they had a pop sensibility and they still kept the crux of the song intact. Bach’s counterpoint stuff does that too. A lot of it is simply that a low tone has a lot of room to play in and will resonate longer. Once you get the air moving, it wants to keep moving, and low tones go through just about anything (and really high tones — this is why marching bands will have a single flute or piccolo player, often, they cut right through all the mids).
I don’t know why I’m even thinking of all this stuff. Olive Oyl and her Tattoo’d Man broke up and I picked up his old bass at their we’re-breaking-up-and-getting-different-places-so-buy-our-old-shit garage sale for 20$, maybe that’s it.
Here’s the band that John Peel called ”always the same, always different”