Organ Tuning

The organ tuning is at Cornet-Ton pitch
(today, A = 465 Hz).

The spiral is to be interpreted as follows:

• The small loop (knot) at the far left is for the lower pitched harpsichord and is ignored.
• The three large loops enclosing a single knot indicate three intervals that beat slowly (once per second) in the 12 semitone range upwards from middle C (one-line octave).
• The three large loops without knots indicate three pure intervals without beats.
• The five large loops enclosing double knots indicate five intervals that beat quickly (twice per second) in the one-line octave. Equivalently, they indicate five intervals that beat slowly (once per second) in 12 semitone range below middle C (small octave). 

Canonical Reading

The canonical reading is a tuning specification in terms of beats per second for fourths and fifths in the range middle C, C#, D, Eb, E, F, F#, G, Ab, A, Bb, B (one-line octave); the beat rates being 0 Hz (pure), 1 Hz and 2 Hz. A possible realisation is given below.

Tuning Circle (Click to Enlarge)