Max Overdrive and Audio Interrupt tighten timing of MIDI and metro events against the signal vector

Max separates its event scheduler from MSP audio computation, which can make timed events (metro bangs, incoming MIDI) drift relative to the audio. Scheduler in Overdrive raises the priority of timed events and MIDI above secondary tasks like screen redraws and mouse input, giving more rhythmically precise timing at the risk of an unresponsive UI if overloaded. MSP signals always outrank Max messages regardless. Audio Interrupt (available only in overdrive) processes timed events immediately before each signal vector, tightening MIDI-to-audio sync; but it only helps with a small signal vector, since Max must wait for MSP to finish a vector before emitting its message. A 1024-sample vector at 44100 Hz means events fire in bursts every ~23 ms; a 16-sample vector reduces that jitter to under half a millisecond.

Examples

With Audio Interrupt on and a 1024-sample vector, a sequence of scheduled bangs arrives in clumps every ~23 ms — audibly loose. Dropping the signal vector to 16 samples makes the same sequence tight. A patch where Max messages trigger MSP sound (e.g. a step sequencer) benefits from overdrive + audio interrupt + small vector.

Assessment

A metro-driven sequencer sounds rhythmically loose when triggering MSP synthesis. Name the two Audio Status options to enable and the parameter to shrink, and explain why a large signal vector defeats Audio Interrupt.