Most flutists know that the modern flute mechanism was invented in 1847 by German composer, inventor, and flutist Theobald Böhm. However, the C# trill key was not added until 1863 by the French flute maker Louis Lot, patented by Laubé in 1909. Böhm-system flutists spent 16 years without the key, and even after its invention to the modern day, it is only found commonly on professional instruments. So what is the C# trill key, and why do we have it?

This optional key is located next to the Bb lever, activated by the right-hand first finger and corresponds to a tone hole on the back of the instrument next to the B key. Though it can take some getting used to, the C# trill key is conveniently located to the left of and slightly higher than the Bb lever, ensuring ease of operation.

So why might you want a C# trill key? This key simplifies some of the most awkward trills and tremolos by moving many left-hand actions to the right hand. For example, the B-C# trill found in Mozart's Concerto in D major, K.314 or Böhm's Grand Polonaise, Op.16. The C# trill key also facilitates the third octave F#-G# trill with great ease. When combined with other trill keys, it simplifies third-octave trills such as G#-A# in Dvorak's Cello Concerto in B minor, Op.104 (Mvt. I) and G-A in Prokofiev's Sonata in D major, Op.94 (Mvt. IV). It can also be used in tremolos when moving from the first octave G, Ab, A, Bb and B to C#.

In addition to making trills and tremolos much easier, the C# trill key enables some special fingerings to achieve colours and dynamics against the flute's natural design, such as soft, high playing. For example, by pressing all the keys in the left hand and adding the C# trill key, we can achieve a soft third octave G#/Ab with good intonation and colour. How about creating beautiful colours on the opening C# of Debussy's Prélude à l'après-midi d'un faune? Using the C# trill key while fingering B gives the note extra resistance, allowing you to explore tone colours with a more secure pitch.

Considering all these benefits, why might you opt out of the C# trill key? Having this key requires the addition of a lever, rod and key. Some people may find this weight difference noticeably uncomfortable when playing for extended periods. With these additions in weight also comes an addition in price, another reason they are found mostly on professional instruments. Though some have speculated that this addition may negatively impact the overall sound of an instrument, reputable flute makers such as Brannen Brothers have compared identical flutes with and without the key and found no noticeable effect on the tone.

There are many benefits to the C# trill key that most would argue outweigh the drawbacks; this key provides more fingering options, making difficult patterns easier and increasing the scope of expressive capabilities. Regardless of which side of the fence you are on, the C# trill key is undoubtedly a valuable addition to the mechanical advancements of the Böhm flute for orchestral, chamber and solo musicians alike.

The C# Trill Key: What is it and why do we have it?

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