Mozart is known primarily as an opera composer who wrote vast amounts of keyboard, symphonic, and chamber music. However, among his many hundreds of works are lesser-known and unknown pieces for instrumentations we don’t normally associate with Mozart, but which in some cases are some of his finest masterpieces (like the F minor organ Fantasia). Among these overlooked works are a few short pieces for the glass harmonica. Given the dearth in glass harmonica players, these pieces often end up being played on the piano. This week I discuss the Adagio for the glass harmonica, K. 356.
The glass harmonica, as we know it, was invented by Benjamin Franklin. Its sound is produced by the friction of wetted fingers on rotating glass bowls and goblets. Although some precursors to Franklin’s instrument exist, it was he who arranged the bowls and goblets in a gradual order according to pitch. Its sound is entirely ambient and agogic, and has virtually no articulation, a bit like speaking only with vowels. Not unlike the arpeggione, it didn’t leave a rich legacy of interpreters and repertoire. But Mozart’s glass harmonica works are not in any way inferior because of the limitations of the instrument. If played on the piano, they benefit from articulation and a dynamic range that the glass harmonica is incapable of producing, letting the listener perceive a lot more detail than can be achieved on a purely agogic instrument. The only slight oddity in playing the glass harmonica repertoire on the piano is that the music is entirely in the high register of the piano, as the glass harmonica lacks a low register. Only treble clefs are used in these few pieces. But then, many works by Mozart and Haydn are centered around the upper register of the piano (even if not exclusively confined to it), given the register of 18th-century keyboard instruments.
The short Adagio in C major is noble and solemn in character, placing it among Mozart’s “edifying” works. Goodness and wholesomeness emanate from the harmonic and melodic traits of the piece, and minor harmonies are rarely heard. The frequent thirds make the music reminiscent of the composer’s writing for wind instruments (Harmoniemusik). One could easily imagine the piece being played by clarinets and oboes. The only aspect of the work that in my mind corresponds to the characteristics of the glass harmonica as opposed to those of either a keyboard or a wind instrument is the time signature of 2/2 (alla breve). Generally, in classical and romantic music and especially in Mozart, the markings of 2/2 and Allegretto imply a more leisurely pace than 4/4 or Allegro. That allows, and even asks for, greater rhythmic flexibility and elasticity. Because of the agogic nature of the glass harmonica, it is impossible to play it with rhythmic accuracy in a proper 4/4 rhythm. The handicaps of the instrument notwithstanding, Mozart’s flawless sense for ornamentation is heard in the repetitions of thematic material. This is one of the qualities that make this piece “unmistakably” Mozartian.
Naturally, playing works originally written for obscure instruments isn’t something pianists do too often, but playing transcriptions and arrangements is. The question we face in this Adagio isn’t too different from the ones we face while playing operatic or symphonic transcriptions: should the characteristics (in the case of the glass harmonica, incapabilities) of the original instrumentation be preserved, or shouldn’t they?