I hate to re-open this discussion, but given that I just saw recent postings about how threads on M1 processors might get allocated to e-cores instead of p-cores, and since there appears to be no control over thread priority through JUCE Thread on Apple Silicon (assuming what was mentioned in FR: Thread-Priority vs Efficiency/Performance Cores is correct) - is it possible that some of my audio processing threads got assigned & dropped priority to e-cores and then were impacted by other e-core threads at same priority such as graphics refresh related threads - thus holding up completion of my audio callback tasks? This might explain why graphics repaint related code appeared to severely impact the audio processing load on my M1 builds and not on the same Intel Mac build.