This song was composed by Giulio Caccini, an Italian composer of the late Renaissance/early Baroque eras. He is one of the founders of opera, and this is one of his most famous madrigals.
The ocarina is made by Kenji Ogawa of Japan, and you can find the accompaniment for this song on his CD, Toy Box 1 for Ocarina.
After doing some research on this song, I was unable to find the composer, but it seems to be a folk song from Catalonia (near Barcelona, Spain), an area rich in musical culture which flourished during the Renaissance.
The ocarina is made by Kenji Ogawa of Japan, and this song is one of many from his album, Toy Box 1 for Ocarina.