Select compression

Seems to be a wave clipper when you increase the input rather than compress it. Output wave should never have harsh clipping or elements of rectification unless you intend it to be some sort of effects unit for music or something. Unless i have misunderstood the circuit.

Yes pip has right. Most simpliest signal compressing device is simple preamplifier with gain limiter or active attenuator controled by some sort of input watchdog who whenever input slope of signal has too fast slope rising time sends control signal to surpress preamp gain or boost attenuator influence to such level that for example avoid overdrive of next amplifier stage. Advanced models have also a frequency watchdog in addition to level one to chose particular frequency band that is over influence of level compression . Scanning for example only low frequency band to avoid damage or limit buzzing sound of overdriven car subwoofers when beat become too expresing.