"The 'supreme head of song' was a poetess"
The 'supreme head of song' is Algernon Charles Swinburne's description of the Greek poet Sappho in his poem Ave Atque Vale ('Hail and Farewell'):
That knows not where is that Leucadian grave
Which hides too deep the supreme head of song.
Sappho was thought to have jumped from the cliffs of Leucadia, an island in the Ionian sea, because of her unrequited love for Phaon.
The poem is in memory of the French symbolist poet Charles Baudelaire.
Ave Atque Vale is also the name of an elegy written by the Roman poet Gaius Valerius Catullus (84BC-54BC) to his brother.
Accept, by custom, what a brother's tears drown
and, for eternity, brother, 'Hail and Farewell'.