Generation gap? What generation gap? Both grunge-fed twentysomethings and their aging hippie parents had something to mosh about last week when news broke that boomer icon Neil Young and X'er faves Pearl Jam were holed up in Seattle recording an album together. The collaboration could be out as soon as this summer, and may be followed by a tour. Young, 49, has already performed with Pearl Jam, and was introduced by PJ front man Eddie Vedder, 29, at his induction into the Rock and Roll Hall of Fame last month. It was after that that the project gained momentum. Young's manager told the L.A. Times: ""They flew to Seattle and three days later they had five songs.''