Saturday's Technical Bit

Just a few words on organ pipes again:

First off…….. the Bass pipes.

I have laid the organ on it’s side to give a view of the five largest pipes.

As they are the largest, they sound the lowest notes. They are wooden stopped pipes; which means that they are tuned by a sliding “stopper” at the top end.

The largest is about 18” long, and in order to get it in the organ case, it has a right-angled bend in it. This bend in a stopped pipe has little, or no noticeable, effect on the sound produced. This is not the case with an open pipe (no tuning stopper).

If the inside “effective” length (between base and stopper) is, say 12”, this will sound the same note as an open pipe of 24” length. This makes stopped bass pipes a better choice for small organs; instead of an open, pipe 4 feet long, we can have stopped, angled pipe of 2 feet to produce the same sound and take up less space.

The five bass pipes on my organ are:- Eb, F, Ab, Bb and C (middle C).

In the key of Eb, we have Eb(tonic),  Ab(sub-dominant) and Bb(dominant 7th) and for good measure there is F(related minor 2nd) and C(relative minor 6th).

This is the best key for arranging, as there are the fewest missing notes.

In the Key of Ab, we are missing the (sub-dominant) Db.

In the Key of  Bb, we miss out on the minors.

In the key of F, we again miss the minors.

If I’m really stuck I can, at a push, arrange in the Key of Db, by using the lowest of the accompaniment pipes (Db) as a bass note.