Q. Do we know who wrote Adon Olam?
A. The content and style reflect the late medieval period. It may not have become popular until the 15th century, when manuscript Machzorim included it among other poems but without stating the name of the author.
A manuscript of the Roman Machzor simply calls it piyyut na’eh, “a pleasant poem”.
From the last line of the poem we get the impression that it was composed as a night prayer, but in time it seems to have become a morning prayer too. The consensus of opinion is that the author, whoever it was, was Italian.
What made the hymn so popular is both the theme – God’s greatness and closeness – and the rhyme and metre, which encouraged almost every synagogue composer to produce a melody for it.
In the Spanish (Sephardi) version there are two extra lines in the poem – rather obviously by a different hand and not of quite the same quality – and it has been suggested that they were introduced in order to fit into the musical scheme chosen by some composer or chazan.