Casella (Divine Comedy)
All that is positively known about him is what is found in Dante's work and it has been impossible to identify him with absolute certainty with any of the Casellas named in contemporary documents.
To whatever is said of him in Dante's work one can add (with some degree of probability) information furnished by the earliest commentators of the Divine Comedy: Pietro di Dante, Benvenuto da Imola, Buti and Landino give him as being born in Florence, while an anonymous early commentary of the Divine Comedy gives him as being born in Pistoia.
Mentions of this Casella in documents probably include a mention (Casella dedit sonum, i.e. "Casella set [this] to music") in Codex Vaticano 3214 that he set to music a madrigal by Lemmo da Pistoia, and a mention of him in a sonnet by Niccolò de' Rossi.
From what is said of him in Purgatorio, 2nd canto, it appears that he was a friend of Dante, that he died before 1300 and that he set to music poetry by Dante himself, namely the canzone Amor che ne la mente mi ragiona found in Dante's Convivio and possibly some other short poems by Dante, and from specifically line 107 in the 2nd canto, it may be possible to infer that the amoroso canto ("amorous song") that Dante connects with Casella is a specific indication that Casella's music was (at least in part) in the monodic style which accompanied Occitan lyric poems, or Italian lyric poems in the Occitan manner.