diapason

There are basic groupings of sound, such as flutes, the human voice, trumpets and the diapason, which is the organ’s own sound.

Feldman was fascinated by the organ's principal pipes that produce the thickly textured diapason sounds that are pure organ, as opposed to the myriad other pipes with, say, flute-like or brass-like characters.

“Oh, Miss Lee, they’ve got the most lovely dresses,” she went on, releasing every stop in a diapason of envy.

The only stops I found available, were a very weak croaking flute, and a quavering deep pedal diapason, of sixteen feet.

The four bars are said by Plutarch to represent the elements, but it is more likely they were certain notes of the diapason.