Composer anniversaries, which the classical music world never tires of observing, are often just an excuse for ensembles to perform music they would have performed anyway. (The really big kahunas get both their birth and death celebrated every 50 years.) But two local choirs are going all out this weekend with a pair of oratorios that represent their composers’ grandest expressions of religious feeling. To honor Felix Mendelssohn (born Feb. 3, 1809), Seattle Pro Musica, under Karen P. Thomas, is performing his vast and rousing Elijah (1846). That story of the Biblical prophet retains not a little contemporary resonance, given its themes of religious conflict and crusading belief. (God vs. Baal—guess Who wins?) The God of Joseph Haydn (died May 31, 1809) was a considerably more benign deity, and Master Chorus Eastside is staging his 1798 The Creation, a picturesque tour through His seven days of handiwork, with instrumentally depicted details from the origin of light to the creeping of the worm. “To match Haydn’s sense of play,” says MCE director Linda Gingrich, the work is being semi-staged with special lighting, blocking, and set pieces representing mountains, animals, and such. The soloists singing Adam and Eve may or may not appear authentically costumed. Elijah: St. James Cathedral, 804 Ninth Ave., 781-2766, www.seattlepromusica.org. $25-$32. 8:15 p.m. Fri., May 8, 8 p.m. Sat., May 9. Creation: Eastlake Performing Arts Center, 400 228th Ave. N.E., Sammamish, 425-392-8446, www.masterchoruseastside.org. $9-$18. 7:30 p.m. Sat., May 9. GAVIN BORCHERT

Fri., May 8, 8:15 p.m.; Sat., May 9, 7:30 & 8 p.m., 2009