Musicologists have speculated: first, that the Adagio in D minor ( JS 12) may have been intended as a slow movement for the Op. 4 quartet and second, that the Allegretto in B-flat major (without catalogue designation) may be an abandoned sketch.
It is the third of Sibelius's four string quartets. The String Quartet in B-flat major, Op. 4, is a four- movement chamber piece for two violins, viola, and cello written from the summer of 1889 to September 1890 by the Finnish composer Jean Sibelius.
