At the same time, the earliest appearances of a paion or hymn of thanksgiving also appear in the Iliad, when after the prayer to avert evil from the Achaeans, a paean is sung, and, in an almost identical line (X.391), Achilles bids the Myrmidons sing the paean after the death of Hector.
To discover the relation between Paean or Paeon in the sense of "healer" and Paean in the sense of "song" it is necessary to identify the connection between ritual chant and the shaman's healing arts. Martin Nilsson oberved:
The curing of diseases everywhere plays an imprtant part and among primitive peoples lies in the hands of sorcerers and priests. There was in earlier Greece a class of seers and purificatory priests which in all essentials fulfilled this function. The art of healing consisted in magical ceremonies and incantations. In later times these were usually called έπφδαί, charms, but in earlier days they were certainly called paeans (παιάν), for Homer speaks of the god, Paieon, who takes his name from them. With the charm was blended the name of the god, and thus the paean became a song of thanksgiving and eventually of victory. In later times Apollo has made the art of healing his own, and after him his son Asklepios took it over.
Previously, L.R. Farnell had referred to the ancient association between the healing craft and the singing of spells, but found it impossible to decide which was the original sense. At all events the meaning of "healer" gradually gave place to that of "hymn," from the phrase Ιή Παιάν.
Such songs were originally addressed to Apollo, and afterwards to other gods, Dionysus, Helios, Asclepius. About the 4th century the paean became merely a formula of adulation; its object was either to implore protection against disease and misfortune, or to offer thanks after such protection had been rendered. Its connection with Apollo as the slayer of the Python led to its association with battle and victory; hence it became the custom for a paean to be sung by an army on the march and before entering into battle, when a fleet left the harbour, and also after a victory had been won.
Musically, the paean was a choral ode, and originally had an antiphonal character, in which a leader sang in a monodic style, with the chorus responding with a simple, informal phrase; however, later in its development, the paean was an entirely choral form. Typically the paean was in the Dorian mode (note that the Ancient Greek Dorian was different from the modern Dorian mode; see musical mode), and was accompanied by the kithara, which was Apollo's instrument. Paeans meant to be sung on the battlefield were accompanied by aulos and kithara.
Two musical fragments of paeans survive from late antiquity: one by Limenius of Athens, and another anonymous. The fragment by Limenius has been dated to 128 BC.