Subsequent studies with Nadia Boulanger, Luigi Dallapiccola, Darius Milhaud, Paul Hindemith, and Philip Bezanson in composition, William Steinberg and Leonard Bernstein in conducting, and Hugo Kortschak and Ivan Galamian on violin took Yannatos to Yale University (B.M., M.M.
As a young violinist, he performed at the Casals Festival and elsewhere in various professional ensembles, including a piano trio, a string quartet, and early music groups with Hindemith and Boulanger.
His only opera, Rockets' Red Blare, to a libretto he wrote himself, premiered in 1971 in a student performance at Harvard University's Loeb Drama Center.
On October 1 and 2, 2011, a completely rewritten score to Rocket's Red Blare received its professional premiere by Intermezzo, The New England Chamber Opera Series at the Agassiz Theater in Radcliffe Yard, Cambridge, MA.
Intermezzo's production was directed by Kirsten Z. Cairns, with Edward Jones conducting the Juventas New Music Ensemble; designers William Fregosi (scenery), Rebecca Butler (costumes), and Winston Limauge (lights); and Singers David Kravitz (King), D'Anna Fortunato (Queen), Gregory Zavracky (Prince), Natalie Polito (The Girl), and Charles Blandy (Jester).