Confounded diphthongs

On Saturday evening, at Reading's Great Hall, listening to Trinity Concert Band, I was reminded of the power of music in stimulating memory (much greater, I'd say, than the overrated Madeleine Effect). Earlier this year I wrote here about my thespian debut:

My own 42nd Street dream centred on the Sergeant-at-Arms in Iolanthe. I was a peer, but I dreamt of  standing in at the last minute for the fellow bass who had that part – not a huge one (I wasn't that ambitious –  he had one song, at the beginning of Act Two [in that YouTube clip the song starts after about 1 min.], as I remember: "the ice-cream slot", as it was archly referred to among the wiseacres of the Cecilian Players [not the chamber ensemble, an amateur operatic society based in SW London in the 1960s and '70s] – the first turn after the interval, when the audience are at their least attentive).  I was going to "Go out there an unknown and come back a st... well, a bit-part player".

And on Saturday, when the band played the opening chords of the Peers' March, I was back in the Questors Theatre, at the back of the audience, ready to process down to the stage. The words of the chorus came back to me:

Bow, Bow ye lower-middle classes

Bow, Bow ye tradesmen, bow ye masses

And with that memory came a memory of the MD ...

<autobiographical_note>
..."Budgie" Byrne, my music teacher (though it wasn't a school production) who, in the days when teachers were allowed to write what they thought in school reports, wrote of me "C+ – has ability but is disinclined to use it musically"...
</autobiographical_note>

...warning us not to enunciate the /ʊ/ of /bɑʊ/ until the last moment (a warning repeated by countless MDs over the next 50 years in other contexts).

One of those MDs warned me about another diphthong (tricky chap, Johnny Diphthong), rehearsing Haydn's Te Deum. This time, it was a diphthong to be avoided; the opening word was not /teɪ/ but /tɛ/:  not having the resources of the International Phonetic Association, she told us to imagine it was spelt teh (at the risk of anachronism I suppose she might have said it rhymed with meh). And that warning too has been repeated by my present MD (as we will be singing the piece, inter alia, at the Great Hall [where I started this post]).

I have mentioned word painting several times before; but one particular instance has caught my attention in the Te Deum. The tritone ....

<autobiographical_note>
(bane of a child violinist's life, especially in the key of Bb if memory serves*, not that I stuck at it for more than a year or two; couldn't stand the noise)
</autobiographical_note>

... is known as diabolus in musica. I don't expect Haydn was ignorant of this. An entry in the Guardian's Notes and Queries section summarises:

...the augmented fourth was the only augmented interval that appeared in the modes used before the emergence of the major and minor scales. Using only the white keys on a piano, the interval of F natural to B natural is the only augmented one (also known as the tri-tone) and was considered so unnatural and discordant in pre-tonal times as to be known as the Devil in Music

There's much more there, of varying  quality and accuracy. Caveat emptor ; I for one don't buy

THIS chord was banned because it was very hard to sing.

The devil's interval

Near the end of the Te Deum, the basses sing  Non confundar – "Let me not be damned" – ending on a B. And there, in the soprano line^P4S , is an F.  F  to B – "the devil's interval". The sopranos' F is a good few octaves above the basses' B, but the devil is hiding there. Sneaky.

Aunty Katy (mentioned many times before) was right: he was always lurking where a good Christian least expected it.

Idle hands, though. I must be getting on.

b

PS: A couple of political clues:

• Regurgitated nasty brioche that he left to make left-winger. (10)
• Not 'ard Brexit – no way; after haggling, very costly. (10)

Update 2016.10.04:14:15 – Added footnote

* Close, but no cigar. I was thinking of the key of F major (which involves a tritone stretch on the A string. (It all comes flooding back: An inch boy, an inch. Don't you know what an INCH looks like? My teacher, a dreadful old woman, was a fan of neither Galileo nor Pythagoras.)

Update 2016.10.16.22:15  – Added snippet of Te Deum score.

Update 2016.12.30.11:45  – Added PPS

PPS: Crossword answers: CORBYNISTA and  EXORBITANT

Update 2017.03.02.16:15  – Added PPPS

PPPS Fixed the link in the footnote, having initially got my Galileos mixed up. I was referring to the father,  lutenist and music theory pioneer – although I can't imagine that the boy didn't assist in his father's investigation of string-lengths.

Update 2017.10.16.15:55  – Added P⁴S footnote

^P4S It's not only the sopranos with that distant F. The bass accompaniment is marching relentlessly towards an F, and gets there in the fourth beat of the bar.