I'm a classically trained pianist who, on occasion, plays keyboard on stage. Though I am told that the latency in a given system is negligible by the tech, I often think I can feel the difference between the immediacy of a piano with that of a keyboard running through a program like Mainstage. Please can you shed some light on how many milliseconds of latency is acceptable and how much is just people like me thinking we can feel a difference when we can't.
Jonathan Ingham via email
SOS contributor Dave Stewart replies: If you're used to playing Hammond organ, electric piano or acoustic piano, the difference between their near-instant physical response and that of a virtual instrument can feel quite dramatic. In order to buy the time to process incoming MIDI data, computers use an 'In/Out Buffer' to temporarily store data, and this can introduce considerable timing delays. At a sample rate of 44.1kHz, setting the I/O buffer to 512 samples gives a delay of around 12 milliseconds (= 0.012 seconds), which though it sounds tiny on paper, many people can feel. I find that a setting of 256 samples (6ms) is acceptable for most situations, but with instruments that use thousands of samples (sampled pianos being the worst offenders), a setting of 256 samples will sometimes create pops and clicks.
As a rule of thumb, a 5 or 6 ms latency feels OK, but anything above 10ms may cause problems when using samples with hard attacks (drums, percussion, piano or clavinet for example). For live playing, you may find that an instrument such as Pianoteq (a modelled piano which uses no samples) may be more up your street than an intensively sampled, multi-gigabyte piano library.
Ultimately, the best judge of whether system latency is 'neglible' or not is the musician, not the technician. If you can feel the latency when you play, it almost certainly exists!