LEWISTON — A dream more than 50 years in the making will come true for Maine Music Society Artistic Director John Corrie when the conductor signals the MMS chorale and orchestra to begin their performance of J.S. Bach’s Mass in B Minor at 7:30 p.m., Saturday, March 25, at the Gendron Franco Center.

The challenging, enchanting piece is without question, the conductor’s favorite and directing it has been a long-held goal.

The piece will be performed again at 3 p.m., Sunday.

The Mass in B Minor, Bach’s most complex piece, is considered his best work and, arguably, the best work ever written by a classical composer. So difficult to master, the work is considered an ambitious undertaking even for professional groups, requiring months of rehearsals and many hours of practice at home.

Corrie wasn’t sure how the MMS musicans would react to the idea of performing the piece, but he needn’t have wondered — they were all in favor of it.

For Corrie, 69, conducting the Mass in B Minor marks the accomplishment of a particularly dear personal goal that was probably forming in his mind when he purchased his own copy of the full score of the Mass in B Minor. That was in 1961.

When Bach was composing, in the early-to-mid 1700s, he was writing what would have been considered the modern music of his day. In other words, he was a rock star.

His genius musical talent, his willingness to explore and to push the limits of the expected and traditional, all contributed to his superlative composing. But, says Corrie, Bach had something else going for him. He was a singer, and his intimate understanding of how the voice worked helped him in creating some of the intricate moves for which his compositions were known.

Bach also had what Corrie calls a “sixth sense” for creating fugues. Fugues were all the rage in Bach’s day. A fugue is a bit like a song sung as a round, but only a short phrase is repeated, each voice joining in at a slightly different time than ones preceeding it. But unlike a round, where the exact same tune is repeated over and over, a fugue involves slight changes in the theme each time it’s repeated. This creates a complex weaving of harmonies as many variations on a simple theme overlap and echo in a marvelous tapestry of sound.

Bach, Corrie says, was known for his ability to spontaneously compose a fugue. He’d engage in a kind of parlor game, where he’d accept a challenge from one of his associates to write a fugue on the spot from whatever notes he was given. And, of course, he would.

Though the Mass in B Minor is complex, it is not unfriendly to the unschooled ear. Bach’s way with “color” and “texture,” created by experimenting with the orchestral instruments or unusual repetition of common patterns of notes, is a modern concept, Corrie explains, and is interesting to listen to.

The MMS orchestra for the Mass includes a full string section, pipes, a tympany, three trumpets, two flutes, two oboes and two bassoons. Corrie urges the audience to notice how the two bassons are used in particular.

Participating in such a demanding project has been a enlivening experience (albeit sometimes a grueling one) for Susan Trask, head of the MMS board and one of two charter members of the chorale still performing with it after 35 years.

But the years haven’t diminished her enthusiasm for singing, or the work she has to do as chairman of the MMS Board of Directors. She loves the feeling of camaraderie, of being part of a diverse group of folks who share a love of music.

She has seen the chorale through its formative years, its expansion years, and its tough times, just before John Corrie took over in 2006.

And now, says the veteran chorale member, she’s part of an organization that no longer has to hold auditions to fill parts. When they have a need for a particular voice, there are more than enough talented singers who are seeing an opportunity to perform with the chorale.