How can I minimise the power consumption of this crossover clipping circuit?
Following @DaveTweed 's comment, a low-power cross clipper has become obvious to me. There are different issues with the circuit now: cross-clipping is heavily dependent upon input amplitude, so if the signal is loud the relative distortion is low, a low-amplitude signal will be dominated by the distortion, if it passes at all. It would be nice to figure out a way of tracking the distortion based on input amplitude...

Circuit

Removing the collector connections of the NPN and PNP BJTs, the circuit becomes:







simulate this circuit &ndash; Schematic created using CircuitLab

Values for R1 - R4 have been adjusted to provide an optimal range of clipping distortion. By increasing R1, capacitors C1 and C2 can be dropped, meaning I can probably use nicer cap dialectrics like film instead of electrolytics.

Behaviour

Changing the value of R4 from 10 Ω to 100 kΩ (as it might be with a potentiometer) wit 10 kΩ steps yields the following behaviour:



With current draw:



So a max current draw of less than 50 µA for a 1 Vpp signal, I'm quite happy with it! I still probably don't understand Class-B / AB amplifier design very well, but this accomplishes my design goals. Thank you to everyone for their helpful comments, and @DaveTweed if you want to submit an answer I will mark it as correct, since this answer simply follows on from your direction.