Billy Joel has added a 21st show as part of his record-breaking residency at Madison Square Garden. The Sept. 25 concert will be Joel's 67th all-time performance at MSG. Joel's previously announced January-July shows are sold out. Citi card members have exclusive access to presale tickets for both the Aug. 20 and Sept. 25 shows through tomorrow via citiprivatepass.com. Tickets for the August and September shows will be available for purchase by the public at 9 a.m. on Friday via ticketmaster.com.