Felix Mendelssohn wrote his Octet in E flat major, op. 20, in 1825. He was only sixteen years old at that point, and he came up with the piece as a birthday gift for his friend and teacher Eduard Ritz (1802-1832). The octet underwent a revision in 1832, and it was premiered in 1836. The score calls for a double string quartet. A standard rendition of the piece takes about half an hour.