I'm not sure how to go about adding sound files to an article this old. But for any string player it is easy enough to experience the sounds for yourself by looking at the Schelleng diagram, and then doing the wrong thing: start a nice note, then slide the bow towards the bridge without increasing the bow force, and it will slip into surface sound after a bit. Some of these sounds are indeed used deliberately for special effects: "sul ponticello" playing is exactly what I have just described, light bowing near the bridge. "Sul tasto" is a way to get a different kind of failure of Helmholtz motion by bowing a long way from the bridge. Sustained raucous sound would be unusual, but a soloist trying to make themselves heard over the sound of an orchestra may push close to the limit and get a "borderline raucous" sound. Much more commonly, you can hear a bit of raucous sound at the start of a "crunchy" or "scratchy" note. So depending on whether Amy produces a crunch or a whistle, she is slipping out of the Helmholtz region in one way or another.

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