Light is dawning! Thank you for the explanation.
You \re welcome.
It should also be said that there are certain compound (mixture) stops which do not break back. For example, the Cornet - which could commence at 12-15-17, 8-12-15-17 or 1-8-12-15-17, depending on the total number of ranks it contains. Of course, there are also examples which add ranks as they ascend the compass, viz.:
C13: 12-15-17
G20: 8-12-15-17
C26: 1-8-12-15-17
Such a stop would normally be engraved 'CORNET III-V'.
It will be noticed that this stop is not of full compass. A Cornet often goes only as low as C26, but there are many examples which extend to G20 or even C13. This is because its primary intended function is as a solo stop and Cornet solos were not usually written to go below C26 - certainly not G20. The reason for this is that generally, any lower than this and the constituent pitches tend to fall apart, instead of cohering into a resultant, reedy sound.
A Sesquialtera is another example which does not break back. A stop of this nature will usually commence at 12-17 and continue throughout the compass of the clavier. The pipes may be wide-scaled flutes, with good blending properties or they may be of a rather narrower scale (for example the North German Baroque Sesquialtera) which is, once again, intended as a solo stop - although naturally it will require the addition of a unison stop (such a s a Rohrflöte or Stopped Diapason) and probably also a 4ft. flute - again, often composed of stopped pipes.
There are also Cavaillé-Coll's
'progressive' mixtures, which also did not break back. Like some Cornet stops, ranks were added at various points in the compass. However, these stops would not normally have included mutations higher than the Tierce. A colleague has stated that Cavaillé-Coll also included the flat twenty-first (1 1/7ft. - the Septième) in such stops. However, I have yet to find an example which has this very audible - and very anti-social pitch in its composition.
There are also higher-pitched compound stops which break back more often, such as the
Cymbale (or
Cymbal - or even
Cimbel or
Zimbel). Whist there are a number of examples which contain a tierce rank at some pitch (perhaps commencing at 33-38-40, as a
'Terz-Zimbel'), many English examples contain only unison and quint ranks. There is a superb example on the Positive Organ of my 'own' church instrument, the composition of which is roughly:
C1: 29-33-36
A10: 26-29-33
F18: 22-26-29
D27: 19-22-26
B36: 15-19-22
G44: 12-15-19
This stop is intended to cap the Positive chorus. When this full chorus (with the
Cymbal) is added to the G.O. chorus, the effect is electrifying. The distinguished organ critic, Cecil Clutton likened it to listening to a large Baroque instrument in some great church in the Netherlands.
Incidentally, with regard to Post Nr. 9 above, the last two breaks should of course read:
C37: 8-12-15-19
C49: 8-8-12-15
For some reason the 'edit' facility becomes unavailable after a few hours - which is not particularly useful. This does not happen on any of the other boards of which I am either a member or a moderator/administrator, and there have never been any security issues as a result of this. Why does this happen here?