A bold organizational move that gave the musicians of the Saint Paul Chamber Orchestra responsibility for their own affairs--and their subsequent decision to have a series of "artistic partners," rather than one music director--has generated interest both locally and nationally. One of these artistic partners (the excellent Scottish conductor Douglas Boyd) led the SPCO concert on February 26, but the real star of the evening was the SPCO itself. The full ensemble of 30-some musicians started the evening with a smile--namely, one of the wittiest of Haydn's 104 symphonies--but the following 1921 chamber orchestra arrangement of Mahler's Symphony No. 4 showed how mesmerizing the group can be. Just 13 players performed music normally tackled by an orchestra of almost 100. Rather than coming off as Mahler-lite, the reduced forces brought the music into intense focus, highlighting each and every player. It was a musical high-wire act that lasted for 50 minutes; the slightest slip in ensemble or intonation from any of the 13 musicians would have instantly broken the symphony's spell. In the final movement of Mahler's Fourth, soprano Heidi Grant Murphy sang of heavenly bliss, but in the preceding three movements, SPCO's players had already sounded positively angelic.