It has been playing the same piece of music by composer John Cage at a glacial pace for nearly 25 years. A rare chord change on Wednesday — from seven notes to eight once an A4 pipe is added — will represent the completion of about 4 percent of the 639-year endeavor of the John Cage Organ Project Halberstadt. The “ORGAN²/ASLSP (As SLow aS Possible)” composition is scheduled to finish on Sept. 4, 2640. “This John Cage project is a good example of thinking ahead for the next generation — thinking outside the box, beyond the completely normal and traditional,” he said. Inheritable “final tickets” for the Sept. 4, 2640 event are already being sold for 2,640 euros ($3,045).