Carmen Saeculare (Roman hymn)

The hymn was sung by a chorus of twenty-seven maidens and the same number of youths on the occasion of the Ludi Saeculares (Secular Games), which celebrated the end of one saeculum (typically 110 years in length) and the beginning of another. The mythological and religious song is in the form of a prayer addressed to Apollo and Diana; it especially brings to prominence Apollo, functioning as a surrogate for and patron of the princeps (Augustus), for whom a new temple on the Palatine had recently been consecrated.

Source: Carmen Saeculare – Wikipedia