Theobald Boehm (1794-1881) was the inventor of the modern flute. He was a very well-known flutist, a virtuoso performer, and a composer of mostly flute music whose works did not go down in history beyond the flute world. Some of them, however, are truly melodically beautiful. As learning tools they are way above the disdain of politically correct connoisseurs. YouTube has some of his best available works: Nel Cor Piu, Opus 4; Le Désir Valse de Schubert, Op. 21; Air Allemand, Opus 22; and La Grande Polonaise in D, Opus 16.
However, Boehm (or Böhm) is mostly celebrated and remembered among flutists for his clever craftsmanship, technical breakthroughs, and theoretical ingenuity which led to the development of the flute as we know and play today. He was the Thomas Edison and Albert Einstein of the flute.
Few additions have changed or improved the flute in the past 150 years. Boehm’s main concept was to create a tube where each hole produced a half-step rather than a whole-step. Previously chromatic notes required combinations of multiple fingers, resulting in a charming unevenness and daunting complexity that constitute the challenge and perfume of the traverso, also known as flûte allemande (French for German flute) or querflöte (German for sideways flute). This is also why most flute sonatas of the time were written in the keys of G major, D major, E minor, B minor.
One riddle that Professor Boehm did not solve was the Bb. This was partially remedied by Giulio Briccialdi (1818-1881), an effervescent Italian virtuoso flutist in his own right. Briccialdi’s work led to the thumb Bb configuration we have today. Another comfort key is the Bb side key or lever. Boehm knew about it, of course, but this side key was sometimes used by him to help the B-C trill or for other duties.
During my 30 years in Orchestre de Paris, I experimented with and used many different fingerings to facilitate certain configurations or to improve my intonation in problematic chords.
For instance I used five or six fingerings for Bb5 and Bb6, plus three for Bb7. However, as a beginner about 70 years ago, I was taught that there were good and bad fingerings. I soon realized that morality and ethics have nothing to do with fingerings. Musicality is the issue, because good can be unmusical and bad more fun.
Good fingerings apply to rules laid down in books by teachers and therefore are deemed indisputable. However, if an alternate fingering feels easier or more in tune, gives you pleasure, and stems from the imagination, chances are the books and teachers will tell you it is bad.
Coming back to Bb fingerings, I personally used the real or long fingering (Th/1000/1004) very little, because after 60 years of practicing the flute, I could not play cleanly from G to Bb or F# to Bb. The reason for this is the awkwardness of simultaneous action of lifting and lowering fingers working in opposite directions. I called this motion Boehm’s Purgatory.
Professionals and teachers mostly use the thumb Bb or the Briccialdi key. It is the most practical fingering for Bb, although teachers sometimes forbid it to their students. (“Do as I say, but don’t do as I do.”)
The thumb Bb works well in any key signature up through four flats and in keys with five or more sharps. However, the Gb6 will not sound with the thumb Bb fingering. For the interval of G# to A# (Ab to Bb) or Bb to G, the side Bb or Bb lever comes in handy because you can hold it down between these connections.
If the flute is not well-balanced in the flutist’s hands, and the left thumb is holding the flute, it is difficult for the flutist to easily move from the thumb Bb to the B natural. However, if the flute is well-balanced on the left knuckle, this sideways move of the left thumb may be made quite easily. If bassoonists commonly work six, eight, or more adjoining keys with the same finger (left thumb), flutists should be able to juggle two.
A few passages work better with the Bb side key such as measures 4-7 before 30 in the third movement of the Sonata in D, Op. 94 by Prokofiev.
Note: The * indicates Bb played with the side lever.
Andante quarter note =69-72
The Bb side key or lever may also be used to stabilize the flute and to control intonation. For example when making a long diminuendo on G in all three octaves, adding the Bb side key to the G fingering (while it is not needed to produce the correct note) has an ancillary (if seldom used) advantage by having at least one finger of each hand on the flute.
Use your imagination for fingerings considering color, ease, pitch, reliability, dynamics, comfort, and pleasure. While they may be alternate fingerings, are they really good or bad? The issue is music, nothing else.