Three thousand amateur and professional singers are gathering at Lincoln Center on Tuesday night for the National Chorale’s 43rd annual sing-a-long of Handel’s Messiah.

Martin Josman, the National Chorale's music director, has been at every sing-in since the inaugural one in 1967. “There are lots of amateur avocational singers, high school students having their first love affair with great choral music, and college students and adults who are sophisticated and sing regularly," Josman says. "And we have older people who used to sing regularly in church or temple or in community groups, and just want to get back in practice for this evening and enjoy singing this marvelous, marvelous piece.”

According to Josman, Handel’s Messiah is a pleasure to sing, but can be challenging to conduct. At Tuesday’s performance, 17 different conductors will lead the audience through the nearly three-hour holiday classic.

“The sing-in is a celebration of choral singing and it was conceived of in that fashion,” Josman says. “So, instead of one person leading the entire evening, we decided that we would use a different prominent conductor for each chorus. It works marvelously well, and audiences enjoy singing under the direction of all of these musical personalities.”

Josman adds that the work sounds full and rich, in part because the audience's voices are mixed. “We don’t have all the sopranos and altos and tenors and basses in separate sections, people are sitting with the folks they came with,” Josman says. “It creates a marvelous stereophonic tapestry. Singers come and they bring their scores of Handel’s Messiah, and they stand and sing lustily, and it’s just an uplifting experience.”

The sing-in starts at 8 P.M. on Tuesday at Avery Fisher Hall.