Troubles on powering two (audio) circuits with single voltage source
The L7809 is operating very close to the edge: it has a 2V dropout voltage meaning it needs +11V input to remain stable. You're giving it an unregulated +12V through a diode so very little margin - any spikes on +12V (due to amp current spikes) may freak out the L7809.
You can increase your margin by:
-making cap at L7809 input larger
-running Q1 collector from 12V (so current draw on 9V is CMOS only - negligible)
-using an L7808 or even L7805
But maybe best to just remove L7809 entirely, run CMOS from 12V too. CMOS is happy at that voltage and will be more tolerant to VDD fluctuations without a spastic regulator in the way.