The hymn contains a famous self description: the poet says he is a blind man who dwells in rocky Chios, a passage ancient readers took as the composer identifying himself, and it is this passage that later tradition used to support attributing the whole work, and eventually the Iliad and Odyssey as well, to Homer, an identification most modern scholars reject for the Homeric Hymns generally even where they accept it is old. The passage is quoted, remarkably, by Thucydides in the fifth century BCE, who cites the hymn's description of the festival at Delos as evidence for the ancient character of Ionian religious gatherings there, making this one of the earliest surviving instances of one ancient Greek author quoting another by name in something like the way an ancient testimonium is used, and confirming the hymn, or at least its Delian portion, was already old and already circulating as an identifiable, citable text by Thucydides's own time.
Performance context matters here as much as authorship: hymns of this kind were composed for recitation by rhapsodes, professional performers of epic verse, at religious festivals rather than for private reading, and the Delian portion in particular fits the Ionian festival at Delos that Thucydides describes, complete with competitions among singers, which several scholars have suggested explains its otherwise puzzling self promotional request that the Delian maidens remember the blind singer of Chios kindly among visitors, a plausible bid by a real, competing performer for future recognition embedded within an ostensibly religious composition.