Attention, music fans: The new John Harbison album has dropped. The Nov. 2 release, titled “Diotima,” features three ambitious pieces from the repertoire of Harbison, the acclaimed composer and Institute Professor at MIT — who The New York Times once called “one of the finest American composers” of his generation, for his “willingness to transcend” prevailing conventions. Two of the works on “Diotima” have never been recorded before: the title track, written for a full orchestra and premiered by the Boston Symphony Orchestra in 1977, and “Milosz Songs for Soprano…