The bassoon that Mozart wrote for was much different than the modern bassoon in that there were only four or five
keys on the instrument, which made some of the semitones and chromatic runs difficult to play in tune. Mozart understood the instrument very well, as he writes most of the solo part in the singing tenor part of the instrument's range, although he does showcase the rich low notes occasionally.
The solo part is still challenging enough for the instrument that excerpts from the concerto are used as audition material for orchestral tryouts to this day. The concerto is written for soloist, two oboes, two horns, and the usual compliment of strings. It is in three movements:
I. Allegro - Mozart shows his mastery of sonata form in the first movement as the orchestra introduces the two themes. The first begins straight away, with the two horns heard prominently. The second theme begins seamlessly after the first and is slightly different in character, after which a short motif leads to the entrance of the soloist, who enters with a decorated version of the first theme. Rapid arpeggios, notes low in the range of the instrument and rapid repeated notes are just a few of the challenges for the soloist. The second theme also gets expanded by the soloist. A short development section leads to a short bassoon solo before the recapitulation. A cadenza for the soloist leads to the final statement by the orchestra.
II. Andante ma Adagio - The bassoon's flexibility as a singing instrument is showcased in this movement. The unique tempo indication means at a moving pace but slowly, a nuanced instruction for the time. The strings are muted, the soloist again plays mostly in the tenor range with a few low notes for the sake of expression.
III. Rondo: tempo di menuetto - The movement begins in the form as well as the tempo of a minuet, but when the soloist enters its clear that this is a rondo. There are two episodes and two short repeats of the minuet before the soloist gets a chance to play the minuet. After a very short solo for the bassoon the orchestra plays the minuet once more and ends the work