Brett's modulatron - external jack carrier signal

[glops]

Based on Brett's schematic below, if I wanted to wire a jack for an external carrier signal and get rid of the 555 would I simply
wire the tip to pins 12 and 13 of the 4066?  I searched through some threads and found one where someone had the 555 osc and
an external jack for the carrier on switch but didn't explain how they did it.  Just wondering if it's as simple as that.