He composed mostly chamber music; about 100 string quartets, string trios and solo sonatas, and over 100 string quintets. Boccherini's string quintets didn't follow the usual instrumentation of the time; 2 violins, 2 violas and one cello. He did away with the second viola and replaced it with a second cello. In the 1790's he got a commission from a guitar playing Spanish nobleman to arrange some of the string quintets for guitar. Boccherini replaced the second cello with a guitar, revamped and arranged about a dozen string quintets.
Boccherini was influenced by the music he heard in Spain, and this influence shows in some of his compositions, especially the final movement of the Guitar Quintet No. 4. This guitar quintet is arranged from two previous string quintets. It is in 3 movements:
I. Pastorale - With muted strings and a gentle guitar accompaniment, the first movement is a good example of the type of music Boccherini was known for. With gentleness, charm, and the slightest touch of melancholy, the music unfolds and leads to the quiet ending.
II. Allegro maestoso - The second movement opens with the cello, which is spotlighted throughout the movement. Boccherini gives a glimpse at what his virtuosity on the instrument must have been as the cello plays solo passages that include extended passages in harmonics. The guitar's role in this movement is as an ensemble instrument that adds to the texture, seldom being heard on its own.
III. Grave assai - Fandango - The finale starts with a short, slow introduction. The guitar is heard more as the music slowly transitions into the fandango. A Spanish dance that developed early in the 18th century, the fandango is a passionate and lively dance for two people. There are fandangos that can be sung as well. It is a dance that is most often played on guitars and is accompanied by castanets, and Boccherini includes parts for castanets as well as the sistrum. These percussion instruments aren't always included in performance. The guitarist in the video at the bottom of the page taps out castanet rhythms on the body of his instrument. The fandango builds in intensity until it ends.