Rhythmic Precision and Perception

I have been thinking lately about the very small differences between playing a note at the proper time and rushing or dragging it. When you really examine it, it's amazing that anybody plays anything even remotely close to "in time." Take this example:

You are playing a Sousa march in cut time at 120 beats per minute (bpm). Since there are two beats per second, each beat is .5 seconds long. Therefore, if you have a string of quarter notes, they happen every .25 seconds. That means that if you are a bit late or a bit early, the most you are likely to be off is only .125 seconds. That's an eighth of a second! Yet we have the ability to perceive it as being late/early or rushed/dragged. When I remind the band to really listen, they can successfully eliminate that .125 second (or less) lag time.

Here's an even more extreme example:

The Jazz Band is playing "Can't Dance" by Joshua Redman. The tempo is about 96 bpm, and since it's a funk tune, the basic subdivision is the sixteenth note, which lasts for only .15625 seconds. I was working with them this morning to play a sixteenth note on the "a" of four a bit later, or as we say in jazz, "laid back." If you do the math, I am asking them to play a note approximately 6/100 of a second later. Usually we think of that kind of timing as occuring in Olympic sports, but even at the high school level, we can perceive the difference between landing on the beat and laying back--a difference so small as to be negligible in most real-life pursuits.

This just shows you how amazing the musical mind is!