Yes, it’s currently 32 bit only. We’ll add 64 bit builds once Raspberry Pi OS 64 bit version reaches maturity and exits beta stage.
The main Pisound functions should work on 64 bit OS anyway. You could compile the button daemon for button functionality and install it from source code:
git clone https://github.com/blokaslabs/pisound
# Change 'gcc-4.9' to 'gcc' in this line: https://github.com/BlokasLabs/pisound/blob/master/pisound-btn/Makefile#L26
# Ctrl+x, then Y to save and exit
make && sudo make install
sudo systemctl enable pisound-btn
sudo systemctl start pisound-btn
This should set up the
pisound-btn daemon so it will react to the button interactions.