Quieter Commercial Ads for Spotify Free on macOS
Spotify Free can be a great service. Unfortunately the ads are a true pain to the ears, especially when you're enjoying calmer music. ComMute for Spotify will adjust Spotify's volume whenever ads are playing.
ComMute lives in your menu bar. On every track change in Spotify, ComMute adjusts Spotify's volume. This does not influence your system volume, so it doesn't interfere with other apps.
ComMute lets you set the volume for ads and songs. Note that Spotify does not allow to set the ad volume all the way to 0 (this halts playback). The menu bar icon shows if Spotify is muted or not: 
There is also a button to play/pause Spotify, and a display of the current song. Click the current song to copy artist, title, and URL to your clipboard, for easy sharing with your friends.
You can download ComMute.app here. Built on macosx-10.15-x86_64 with Python 3.9.9, tested with Spotify for macOS (Intel) 1.1.76.447.g11f432d8. You'll probably have to accept third-party apps. Or clone git, pip3 install rumps and run commute.py.
I don't have an M1 mac; you can probably use Rosetta on the Intel-app above. Or clone git, pip3 install rumps and run commute.py.
ComMute watches for creation of the file ad-state-storage.bnk.tmp in ~/Library/Application Support/Spotify/Users/<spotify user>/. This file is created every time Spotify changes track, which triggers ComMute to request the current track info with Spotify through an AppleScript request. Depending on the track info, ComMute sends another AppleScript request to update the volume setting.
Settings are stored in ~/.config/ComMute.conf. The file format is very simple: <watchfile>\n<ad volume>\n<song volume>
Thanks to Simon Meusel for the documentation of his previous work: https://github.com/simonmeusel/MuteSpotifyAds (discontinued)