I don’t know what 75 kbps opus sounds like, but I can tell you how 32 kbps sounds. Versus mp3 at that bitrate, it sounds actually listenable, while mp3 sounds like you’re underwater.
All things considered, the Spotify songs probably sound fine at 75.
I can only speak to what a 75kbps mp3 sounds like, but unless Opus is like 3x+ better at compression, it’s going to sound like complete dogshit.
https://listening-test.coresv.net/results.htm#list10 via https://opus-codec.org/comparison/
It is that much better.
Opus @ 160 kbps is like MP3 at 320 kbps IIRC.
I don’t know what 75 kbps opus sounds like, but I can tell you how 32 kbps sounds. Versus mp3 at that bitrate, it sounds actually listenable, while mp3 sounds like you’re underwater.
All things considered, the Spotify songs probably sound fine at 75.
I encode my music to opus 96kbps for my phone, and it sounds great. I can’t tell the difference between that and the original on Sony xm3s.