Phase 90 - C12 purpose and increasing headroom

[vondran]

A common script mod includes removing C12.  I noticed that one review on Harmony Central stated they found it to be warmer with C12 still in.  What does C12 actual do?

Second item is I notice some distortion when hitting notes harder.  I see that the Q1 pnp emitter is connected to the bias voltage used throughout the circuit.  That seems like it would cause clipping as the signal at the base of Q1 will swing above the voltage at the pnp emitter.  Wouldn't it be better to connect this emitter to the supply voltage?