Written about the same time as the Adagio and Rondo for glass harmonica and chamber ensemble in 1791, this brief and beautiful piece is more of a song than an elaborately developed composition, but it is nevertheless a touching work that features the crystalline and breathy sustaining qualities of the glass harmonica. These sustaining tones exhibit a timbral range from the angelic, transparent upper tones to the chesty and breathy mid-ranges especially noticeable on the diminished-seventh chords in the middle section of this piece. Benjamin Franklin's mechanized version of the glass harmonica (an improvement over the table-top glasses arranged in geometric patterns) with its spinning circular glasses driven by a sewing-machine-type foot treadle, was played by rubbing the rims with water-moistened fingers, and was the instrument that Mozart used. Franklin enjoyed playing Scottish folk melodies on his instrument in Philadelphia accompanied by his wife on the harpsichord.

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