Tonight at 7:30 at Severance Hall, the Cleveland Orchestra plays selections from Haydn, Hummel and Schubert. Critics consider Haydn's Symphony No. 104 ("London") to be one of his best pieces. Michael Sachs, the Cleveland Orchestra's principal trumpet player, will perform Hummel's Trumpet Concerto. The concert repeats tomorrow and Saturday, and guest speaker Emily Laurance gives the pre-concert talk tonight and Saturday. Check the orchestra website for ticket prices. (Niesel)