When it comes to certain organs, does size really matter? You bet, if you’re talking about the largest church pipe organ in the world, which happens to belong to First Congregational Church, right here in Los Angeles. At five manuals, 352 ranks and 20,417 pipes, the longest of which is a whopping 32 feet, it’s one big monster. And “one” is a relative term; the First Congregational organ is actually two organs — one in the front and one in the rear of the chancel, plus smaller “divisions,” or parts of organs, on the sides. The two organs are connected and can be played individually or simultaneously. Anyway, if you’ve always wondered how the heck an organ works, you can find out this weekend, when the church hosts an “organ crawl” of the Great Organs, which will reveal all the secrets of this musical marvel. You’ll learn all about stops — the components that admit pressurized air (wind) to a set of pipes — like the bourdon, or the chimney flute, or the night horn or the trompette. You’ll explore ranks — the set of pipes that produces a certain timbre — and the organ’s winding system, including fan blowers and reservoirs. By the way, here’s a little organ trivia: The loudest organ stop in the world is the Grand Ophicleide on Atlantic City’s Boardwalk Hall Auditorium organ. They say that the former organ curator was careful to warn the stagehands when the Grand Ophicleide was going to be used, so they wouldn’t get their ears blown off. First Congregational Church of Los Angeles, 540 S. Commonwealth Ave.; Sun., March 30, 2 & 4:30 p.m.; $10 advance (before March 28), $15 door (based on availability). (213) 385-1345.