The Boston Conservatory hosts a two-day Boston Harp Festival with performances, panels, and master classes. The event culminates with a splendid Sunday concert: Astor Piazzolla’s “The History of Tango,” performed by Ann Hobson Pilot, recently retired Boston Symphony harpist, and Boston Symphony Orchestra (BSO) violinist Lucia Lin; Schubert’s “Arpeggione Sonata” (written for the long-obsolete string instrument and piano), arranged for cello and harp by Ina Zdorovetchi and performed by the arranger and cellist Holgen Gjoni; Debussy’s Dances for Harp and Strings, played by Ms. Pilot’s BSO successor Jessica Zhou; and Ravel’s Introduction and Allegro, played by harpist Ursula Holliger with flutist Ona Jonaityte, clarinetist Rane Moore, and the three-year-old Arneis String Quartet.