Interpretation usually isn't as fast as speech. If you watch an interpreter you'll notice that when the speaker pauses the interpreter is often still going. O

Interpretation usually isn't as fast as speech. If you watch an interpreter you'll notice that when the speaker pauses the interpreter is often still going. Often it can lag by a few seconds or more, depending on what's being said. If they didn't interpret the gestures, they'd fall out of the stream and be harder to understand. For example, if a professor says "You can see here [points at figure A on the board] that ABC and here [points at figure B] that XYZ..." you need to have those "points" in the right places to understand them. Certainly not all gestures a musician makes are significant, but some probably are.