Maestros ReadyTwo last minute substitute maestros on the Philadelphia Orchestra podium this month were anything but knock-offs. The celebrated pianist Helene Grimaud, was to perform with the orchestra and Yannick Nezet Seguin conducting on the Dec. 5-7 series of three concerts. Nezet-Seguin was in Canada, advised by doctors not to fly because of a severe sinus infection.The always fun to watch Michael Tilson Thomas graciously filled in for him. As he has shown before, Tilson-Thomas taps hidden qualities of the Philadelphia Orchestra in unpredictable ways, not to mention his deportment — a cross between conductor serious, wry and total funsies. Grimaud was scheduled to play Brahms Piano Con. No. 2, but changed the program to Brahms Piano Con. No. 1. Whether or not these programs changes led to the sterile opening Brahms first movement is unclear. There is a long symphonic opening and Tilson-Thomas turned up the sonic intensity right away. Grimaud's entrance was subtle and fine, but for most of the movement she seemed too much in her own wind-up zone (and literally, Grimaud oscillates her body before playing denser sections). Some of the passages sounded like the orchestra and the soloists were in different rooms. Helene Grimaud (ph: Deutsche Gramophone) Soon enough though, everything interlocked in the last two movements, with Grimaud and these players essaying luxurious and exploratory Brahms. Grimauld compelling accented the undercurrent Germanic pulse of the work. The pianist played some passages in the old style, with palm raised and fingers rigid, pounding the keyboard, but not for show, and the technical dexterity of the runs just transported.