"In ableton we don't have the option to freeze grouped tracks, which is annoying. There is a workaround though.
1) Create new midi track
2) Add Compressor
3) Open sidechain settings
4) Select Bus that you want to freeze
5) Click on the headphones that allow you to hear the sidechained signal
6) Create an empty midi clip that aligns with the section of the group audio that you want to freeze
7) Make sure the EQ on the compressor is off as not to interfere with the signal