From www.mutopiaproject.org

The Partita in A minor for solo flute, BWV 1013, is a partita in four movements composed by Johann Sebastian Bach. Its date of composition is uncertain, though on the basis of its advanced playing technique, which is more demanding than in the flute part for the Fifth Brandenburg Concerto, for example, it must have been written after 1723. The title, however, is the work of 20th-century editors. The title in the only surviving 18th-century manuscript is "Solo p[our une] flûte traversière par J. S. Bach".
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