The best ticket in town for classical music this summer is one that will take you to hear Nelson Freire play piano concertos with David Zinman and the Baltimore Symphony Orchestra. Tonight at 7:30 the great Brazilian pianist plays the Mount Everest of piano concertos, the Brahms Second Concerto in B-flat. The remainder of the program is Brahms' popular Symphony No. 3. Tickets are $14 and $21. For further information, call (410) 783-8000.