This week’s major events are all of the vocal variety, some accompanied by orchestra on a vast scale and others in more intimate settings. More options, including a bevy of free concerts, can be found after the jump.

>> At the top of our list are the first National Symphony Orchestra concerts (October 16 to 18) conducted by the gifted Iván Fischer, featuring the third symphony of Gustav Mahler (pictured) in the Kennedy Center Concert Hall. German mezzo-soprano Birgit Remmert, who gave a promising performance in the work for David Zinman’s Mahler cycle, will be the soloist. Singers from the University of Maryland Concert Choir and the Children’s Chorus of Washington will also perform in this grand “summer’s dream,” a work that Mahler once described as “an enormous laugh at the whole world.” Tickets: $20 to $80.

>> Just as Mahler’s third symphony epitomizes its era, the turn of the 20th century, Leonard Bernstein’s Mass, an outrageous “theater piece for singers, players, and dancer,” incarnates its time, 1971, when it was commissioned for the opening of the Kennedy Center right here in Washington. The hippies have taken over the Catholic Church, and while the result is nowhere near as profound as Mahler’s third, the work is performed rarely enough that this week’s performances from the Baltimore Symphony Orchestra (October 16 to 18) are a must-hear event. If the trip up to Baltimore is out of the question, the BSO will bring the work back to the Kennedy Center on October 26 at 4 p.m.

>> One of the best choral ensembles in the world, Collegium Vocale Gent from Belgium, will perform a delectable program of music by Haydn, led by fortepianist Kristian Bezuidenhout, on Friday (October 17, 8 p.m.) in a free concert at the Library of Congress. If you cannot reserve a ticket through Ticketmaster, show up early to wait on line for an unclaimed seat.