diapason

n.

1. A full, rich outpouring of harmonious sound.
2. The entire range of an instrument or voice.
3. Either of the two principal stops on a pipe organ that form the tonal basis for the entire scale of the instrument.
4. The interval and the consonance of an octave.
5. A standard indication of pitch.
6. A tuning fork.

[Middle English diapasoun, from Latin diapāsōn, the whole octave, from Greek dia pāsōn (khordōn), through all (the notes) : dia, through; see dia- + pāsōn, feminine genitive pl. of pās, every.]

In English, an organ stop (the fundamental sound of an organ); it may also denote the range of a voice or instrument. In French it may refer to the scaling of a string or organ pipe or to the distance between the finger-holes of a wind instrument.

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/dye uh PAY zun/  
1 a) a burst of harmonious sound  b) the principal foundation stop of an organ  c) (i) the entire compass of musical tones (ii) range, scope
2 a) tuning fork  b) a standard of pitch

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