Here is a new project I've been working on, a comparison of historic flute types on two Bach Siciliano's, one from the E-major Sonata VI, and one in G-minor from the E-flat major Sonata II, by J. S. Bach.
Each of these will be played on three different flutes:
1. a Baroque one-key traverso in A=415, similar to the flutes which would have been played at the time that Bach wrote the Sonatas.
2. a blackwood 6-key simple-system flute at standard pitch, similar to the flutes which would have been played in the nineteenth century.
3. a modern Boehm-system silver flute at standard pitch, the predominant flute found in bands and orchestras from the very late nineteenth century to the present.
First, the G-minor Siciliano :
And then the Siciliano from the E-major Sonata:
On the Baroque traverso, you have six tone holes for the diatonic notes of the D-major scale and one key for E-flat / D-sharp; these roughly to the open strings of a stringed instrument such as a guitar as they resonate in a way which the other notes of the Baroque flute do not. Chromatic notes are obtained through "forked" or cross-fingerings which involve closing additional tone holes below the open hole for the note to flatten the note by approximately a semitone. The quality of the notes produced in this way are "shaded" or "veiled," and thus they correspond loosely to the fretted notes of a guitar. In addition, there are different ways to finger some chromatics relative to their position in the key; thus, on the Baroque flute, there are two different fingerings, one for A-sharp, and another for B-flat--which you use depends on context. These give each key a characteristic and unique sound on the Baroque flute, which composers used to exploit to good effect--an effect, sadly, completely and utterly lost on the modern, equally-tempered Boehm-system flute. A major defect of the Baroque flute is that there is very little difference in F-sharp and F-natural other than the mindset of the player; in pitch they are actually quite close, which is one thing which makes the E-major work difficult. The G-minor Siciliano lies well on the Baroque flute and is only moderately challenging. By contrast, the Siciliano from the E-major Sonata is very challenging and is very much a work in progress.
Keys began to be added to the transverse flute for the purpose of making stronger in character the chromatic notes and also fixing some of the pitch problems noted above; one of the most valuable keys on the keyed flute is the F-natural key, allowing the diatonic F-sharp to be brought up closer to just tuning pitch; the F-sharp on the Baroque flute has to be made very flat deliberately so that the cross-fingered F-natural can be made to work. Both Siciliano's are moderately challenging on the keyed simple-system wooden flute. The G-minor is approximately the same level of technical difficulty as on the Baroque flute; the E-major / C-sharp minor Siciliano is much easier on the keyed flute than on the Baroque traverso, though it is still certainly challenging, and, as above, a work in progress.
The modern flute with its complex key mechanism of open and closed pads and large tone holes was invented by Theobold Boehm in 1847. This flute, unlike any which came before it, uses mathematically-derived sizes and positions for the tone holes for each chromatic note of the scale, and is thus as acoustically accurate as any flute yet made. This flute plays with equal ease in any key, although the different characters which each key had on the older wooden flutes are unfortunately lost. Both Siciliano's lie quite nicely on the Boehm-system flute, and both are far less technically challenging on this flute than on either of the wooden flutes. The Boehm flute is also known for its purity of tone and its capability of being at all volume levels from extremely soft to extremely loud.