It’s slightly confusingly phrased, but the full sentence is:

> The trombone is the only brass instrument in a classical orchestra […] where the main mode of pitch control is by moving the tuning slide.

Which is correct.

I had the same confusion - I'd move the [...] to the following sentence.

jeffbee 2 hours ago | parent | prev [-]

Oh, I read that as an independent statement, rather than one qualifying the first.

You read "where the main mode of pitch control is by moving the tuning slide" as an independent statement? What does that mean on its own?

	▲	jeffbee an hour ago \| parent [-]
		The interrupting parenthetical was so disruptive to the sentence that I thought it said, essentially, "The trombone is the only brass instrument. Parenthetical. The trombone is played by moving the slide."