[Engelbach describes in Letter XII, in a long comic account, visiting his friends Don Ignazio and his spouse Donna Anna, finding only Donna Anna at home]  

[Letter XII] Donna Anna now sung the little air, "Sul margine d'un rio," with such tasteful simplicity, and accompanied her fine voice with such well selected chords of harpeggios, as to convey no mean idea of her proficiency in music. We are astonished at the meretricious tirades of a prima donna, by which she endeavours to drown the simple melodies of a Salieri, Päesiello, or Cimarosa, in order to shew her skill to greater advantage; but the tasteful delivery alone of the simple strains of a good composer finds its way to our heart and our feelings. Donna Anna's song was worth to me all the bravura's of a Mara or Banti. When it came to my turn, I proposed to sing  a duet, which was agreed to. She produced the charming duet from the "Cosa rara,"  and offered to play the accompaniment on the piano-forte. This proved a great treat to me; indeed, often as I have heard it on the best of stages, I never liked it so well as this time, when I was a party concerned in the performance.