Some of the pianists, part of a contingent of 50 led by Chinese maestro Lang Lang, during rehearsals last night in preparation for the Sing50 concert tonight at the National Stadium. The musicians, aged seven to 52, will all play on 50 Steinway-designed Lang Lang baby grand pianos. After the concert, all the pianos will be pledged to schools and institutions as part of the Sing50 Fund's Adopt-A-Piano initiative.