How do you fill a massive cathedral with sound? A really loud organ. But, if the organ is too loud, how do you accompany the choir? Easy – build another organ.

Believe it or not, it is not uncommon for large churches to have more than one organ. Even so, there’s not exactly a wealth of music written for two organs. First of all, these organs tend to be placed far apart (there’d be no point in putting two organs next to each other); this means that they two organists would struggle to stay together, musically. Second, these organs tend to be designed with very different things in mind (there’d be no point in building two identical organs in the same building); one will often be the “main” organ for solo repertoire, while the other will be a “choir” organ for accompanying. Or, one will be designed for Baroque repertoire and the other for Romantic, and so the two instruments would sound like oil and water.

There is, however, a unique piece for two organs and choir which makes a strong argument for this instrumentation – the Messe Solemnelle of Louis Vierne, longtime organist of Notre Dame. The choir sings with the softer organ in the chancel, and the loud organ gets the play the fun parts, a football field away, in the west gallery.

French organs are known for their fiery, dark, thunderous sound (they are also known for never, ever being in tune). I often wonder what it was like for a 19th century French farmer to come to the Paris and hear the organ at one of the cathedrals. I imagine they may have needed new underpants after the experience.

Things I love about this video: 1) this is a REAL MASS, not a concert performance; 2) The French mispronunciation of Latin; 3) you can hear the two organs get out of sync with each other if you listen carefully; 4) the last chord is held so long that you can see the singers taking extra breaths to get through it.