Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
But, wherever the dancers made their appearance, there appeared also the musicians or--which was in the earliest times the same thing--the pipers. They too were never wanting at a sacrifice, at a marriage, or at a funeral; and by the side of the primitive public priesthood of the "leapers" there was ranged, of equal antiquity although of far inferior rank, the guild of the "pipers" (-collegium tibicinum-(2)), whose true character as strolling musicians is evinced by their ancient privilege--maintained even in spite of the strictness of Roman police--of wandering through the streets at their annual festival, wearing masks and full of sweet wine.
2. Cf. I. XIII. Handicrafts
While dancing thus presents itself as an honourable function and music as one subordinate but still necessary, so that public corporations were instituted for both of them, poetry appears more as a matter incidental and, in some measure, indifferent, whether it may have come into existence on its own account or to serve as an accompaniment to the movements of the dancers.
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Reference address : https://www.ellopos.net/elpenor/rome/1-15-art.asp?pg=3