The latest EOCS magazine is well worth joining the EOCS for . . . Despite its name implying an exclusive interest in electronic organs, this is really not the case and most members enjoy playing pipe organs whilst possibly building electronics, and pipe instruments, at home. A good example of this duality was the last Southern regional EOCS installation where we experienced a (dissapointing in my opinion) electronic instrument together with a superb Wurlitzer installation which many members enjoyed despite classical preferences. The Wurlitzer console concept and registration is quite bewildering for those of us with only classical experience.
However, I diverge: the magazine makes fascinating reading and with the use of electronics in pipe organ actions nowadays, there is reason for a broad interest in the subject with universal keying and control systems under development and some electronic computer developments that will send the makers of the Hauptwerk systems running for cover . . . But most importantly an article "A splash of Tone-colour
" the issue of harmonics is examined by Trevor Skeggs. He looks at the frequencies of the harmonics of A=110Hz and in the course of examining issues of constructing waveforms by squarewaves and their harmonics examining how the irritatingly beating 7th harmonic can be eliminated.
The 7th Harmonic is known as the flat 21st as it is out of tune in our tempered scales. Similarly the 11th and 13th Harmonics are very discordant and Trevor points out that it's on account of this that an organ, electronic or pipe, should be voiced with lower 11th harmonic content in lower notes to avoid adding to a diminished chord on accound of the 11th harmonic of any root falling a quarter-tone short of 3 octaves plus a diminished fifth.
He comments that the oboe is not everyone's favourite instrument on account of its predominant 7th harmonic and it's apparently on account of the 7th that classic music theory guides one not to "double" a third of a major chord in another octave. He quotes a website where examples of tones are given that one can listen to http://sethares.engr.wisc.edu/xentone.html
commenting that timbre and the scale being used is a complex interdependance - and certainly I'm aware of this in giving a piano different resonances by reason of bass tuning in unequal temperament.
On account of this, knoweledge within the society goes even to theoretical considerations of which even pipe organ builders would benefit and for this reason I encourage people to join.
PS There's also guidance from a forum member here who is also an EOCS member for anyone wanting to build a home instrument on the cheap of using old circuit boards from redundant Johannus analgue electronics. . .