Clarinet Concerto in A by Mozart, K622

Mozart’s Clarinet Concerto K622 falls into that very group of works whose rich, yet today
mostly revealed background captivates the attention of scholars and clarinetists alike. Being
at the same time one of the greatest masterpieces of the western music, its highly dynamic
‘non-music’ aspect gets on its value even more rapidly. Long-time debated issue of Concerto’s
authentic text and the corresponding instrument stands in the center of that topic. It is well
known today that neither of these – the way we have been accepting them for more than a
century and half – correspond to their originals to the extent that the meaning of work changes
dramatically.
At the end of his life in 1791, Wolfgang Amadeus Mozart (1756–1791) wrote the Clarinet
Concerto as his only piece for the clarinet solo, his last instrumental work, as well as one of
his last works altogether. He noted the piece in his own personal files written during the last
ten years of his life, as penultimate, followed only by the Masonic Cantata K623.
In order to be able to follow the creation of the Concerto we must go back to the year 1784. It
was then that Mozart met Anton Stadler for the first time (1753-1812), the clarinetist
performing one of Mozart’s serenades for wind instruments. Stadler's joining the Mason’s
lodge was the beginning of their friendship. In the meantime, around 1787 Mozart wrote a
199 bars long sketch of the Allegro in G–major K621b for a scarcely known instrument
called a basset horn. For some reason, he did not write any more of this piece at that time.
However, he returned to the sketch around mid-October 1791, but this time he gave up his
idea of the Concerto for the basset horn. Instead of that, he transposed it into A–major,
slightly modified the orchestra scoring and completed it as the first movement of the
Concerto for a special type of the clarinet which will later be named as a basset clarinet. Prior
to Concerto in 1789, Mozart wrote a Clarinet Quintet which was also conceived for the basset
clarinet and dedicated to Stadler.
But, the existence of the basset clarinet and the fact that both, Concerto and the Quintet were
originally written for the basset clarinet, so not for the normal clarinet, are the facts that have
been unfolding only for the last sixty years. Until then the Concerto was being performed on
a normal clarinet, and upon the moment there was little doubt that it shouldn’t have been so.
The basset horn, the instrument Mozart first intended his Concerto to, was a clarinet auxiliary
instrument with a distinguished feature of descending to low C. It was not very handy to play
on, and it was not flat like the clarinet, but curved. Only a few composers wrote for this
instrument. Mozart being one of them, wrote some of the finest pieces for the basset horn, in
particular, solos in the Magic Flute and in the famous Requiem.
On the other hand, there was a basset clarinet, a unique instrument which combined features,
both of the clarinet and the basset horn. Anton Stadler was quite certainly involved in its
construction by fitting the clarinet with extra keys which extended its compass downwards by
four semitones all to the low C – a feature typical for the basset horn. It is to assume that the
features of this new clarinet gave a boost to Mozart to write a Concerto for it, using the
earlier mentioned sketch of the Allegro for the basset horn.
However, the basset clarinet as an extremely rare instrument, went out of fashion soon after
Mozart’s death, therefore when the publishers in 1801 first published the Concerto, they
arranged it for the normal clarinet. Since Mozart’s manuscript was in the meantime lost, the
Concerto continued to be played in this arrangement long after. The same thing happened
with the Quintet which was arranged for the normal clarinet and the autograph of which
cannot be traced to this date as well.
Mozart’s autograph of the Allegro’s sketch in G–major that he applied for Clarinet Concerto,
emerged in 1951 in the Swiss town of Winterthur, having become known as Winterthur
Fragment. Since the Sketch is in its contents basically the same as the Concerto’s first 199
bars, with the only difference being transposed into A-major, it proved to be a critical source
that confirmed Kroll and Dazely’s observations. It showed that the clarinet line indeed
descended to low C on many of occasions, including the usage of chromatic notes C# and D#.
First contemporary performance of the Concerto in the text reconstructed by Czech clarinetist
Jiří Kratochvíl took place in Prague in 1951, exactly 160 years after the birth of the work and
presumable Stadler’s premiere of it also in Prague. It was in Prague again, in June 1956 at the
International Mozart Conference, on the occasion of Mozart’s 200th birth anniversary, that the
reconstructed version of the Quintet was performed for the first time. Kratochvíl, the author
of several papers on this topic, was himself the performer this time. He coined the term
basset clarinet which so well describes the nature of the instrument that connects the clarinet
and the basset horn.

http://en.wikipedia.org/wiki/Clarinet_Concerto_(Mozart)
http://drfeezell.com/smu/MUTh3350mozartclarconck622ianalysis.pdf