Mute groups

Do they work on an instrument level or do they just affect the samples triggered in a column/track

I have the same instrument playing on 3 tracks and the mute group doesn’t seem to be cutting off the samples…

Mute groups work on a per-track level. Here’s a post by taktik:
https://forum.renoise.com/t/done-b4-b5-mute-groups/39991