Pianoteq is highly dependent on CPU performance. This to me sounds like a CPU performance tuning issue more than anything (but yeah there could be background processes also stealing CPU cycles).
I am not sure how Mac OS X handles frequency scaling. But even with HWP (hardware-controlled CPU frequency scaling, which Intel calls "speed shift"), P-state transitions occur in 1-30ms, which is still much too laggy to prevent CPU overloads. CPU scaling is currently too reactive and laggy to CPU load to be of use in preventing CPU overloads. One of the problems I think is that while DSP capacity is heavily dependent on CPU frequency, CPU frequency scaling isn't very sensitive to DSP load. Because it is relatively slow to scale and ignores DSP load, the CPU frequency often doesn't scale until after an overload occurs, or even doesn't scale at all. I don't think Mac OS X has DSP-sensitive proactive scaling algorithms. The closest I have seen to anything like that is http://rg42.org/oss/jackfreqd/start
In short: 1. Don't expect any better low latency throughput performance than your baseline frequency (don't expect frequency scaling to provide enhanced performance) and 2. Adjust your baseline frequency to your performance needs.
My performance index on a Core i5 8265U can vary from 26 - 130 based on what baseline frequency I choose (800mhz, 1600mhz, 2000mhz or 3800mhz) based on power management settings. I have to be very careful with polyphony or sample rates at the lower frequencies. At the higher frequencies, as someone else stated, I can do glissandos with the sustain pedal down, get up to 256+ polyphony at 44.1khz and still not worry about CPU overload.
What does the performance tab of the settings menu indicate (CPU frequency, performance index, etc)?
I am not familiar with OS X power and CPU performance management. Other Mac OS X users may be able to pitch in as to the performance tuning they do.
