This gorgeous new (2006) complex of music space has been highly successful. The performances are many and varied - suiting every taste and pocketbook: classical to folk to dance to new music, Euro 150 to free.
Many of the US's top artists perform here. See the English website http://www.inromenow.com/ for events. It's easier to navigate than PDM's (as it's called, or sometimes it's called just the Auditorium).
Whether or not you're going to a performance, the complex is worth a visit. It's in the Flaminio district, a short tram ride from Piazza del Popolo. Renzo Piano, one of Italy's best known international architects, hit his stride with these buildings. Piano also designed the New York Times building in New York City that opened earlier this year and the Los Angeles County Museum of Art's large addition, that opened last year. But we think Parco della Musica is another degree better than his commissions in the US. (It's in Rome the Second Time as a music venue, Chapter 7.)
You can also get food and drink here (and in the adjacent Flaminio neighborhood - in Rome the Second Time, Chapter 8).
Take a look at the basketball stadium, Pallozetto dello Sport, as you walk from the tram to PDM. The Pallozetto was designed for the Rome 1960 Olympics by one of that era's most well-known Italian international architects, Pier Luigi Nervi, a master with concrete - we were taken to the Pallozetto as college students by our Stanford art prof who was trying to get us to appreciate modern architecture (wow, he got what he wanted from us!).