This is purely a bash script.
Uses dbus, applicable for systems using PulseAudio. Only works while using Spotify client (doesn't matter how you install it) and not web browser.
Mutes and unmutes Spotify within 1 second of start and end of Ads.
To use just run mute_spotify_timer.sh either using terminal or Alt + F2 launcher or just add it to list of system Startup Applications. To allow monitoring the ongoing status, run adfree.sh as a Startup Application, or with bash adfree.sh. It creates a new background tmux session called adfree, which can be connected to with tmux a -t adfree.
In adfree.sh, you may specify respawn=true
I'll make this more efficient when I'll feel free. Meanwhile you can send Pull Requests!