That's part of it. Intuitively (i.e., not scientifically), I think the part that you're missing is the dynamic element. That is, backpressure is not just static resistance, but it changes dynamically as the breath input changes with the volume and frequency of the note. And the relationship is not necessarily linear. In effect, backpressure is more like impedance than resistance.kokopelli wrote:My best description of what backpressure is would be how hard you have to push the air through the instrument.
For example, take a Copeland whistle, which has low backpressure. There's a certain light resistance toward the bottom end. But as you move upwards and increase breath pressure, the perceived resistance doesn't increase greatly. Which can make hitting the right pressure tricky, with a tendency to overblow. Whereas on a Burke, say, the increase in backpressure seems more proportional to the ideal forward pressure for a given note, giving the impression of less breath control effort on the part of the player.