"It is almost a transitional piece into his later, more spiritual, music. It has a lot of great rhythmic writing, plus lovely melodic writing in organ and orchestra."
Were the pedal parts hard?
"No, the pedal parts are pretty straightforward," he said. "The keyboard parts are more active and challenging. Sometimes, the pedal parts move in arpeggios from top to bottom or bottom to top, but not much."
Organs offer a huge variety of sounds from all the different combinations of pipes the player can combine. DuBois will be playing an electronic instrument that reproduces the multitudinous variety of sounds of a regular organ, but the challenge is the same. How does one get an organ to sound like Poulenc wanted it to sound? Did he specify a lot of sounds?
"In the score, he did specify types of sound. It is up to the performer to realize the French sound. Those organs in Poulenc's day had fiery reeds and colorful solo sounds, whether they're reeds or various harmonics. Depending on the stops available, I have to play with the organ to find the sounds that work."
If there is an organ work that symphonic audiences know well, it is Saint-Saens' Symphony No. 3, with Organ. DuBois says it is not an organ concerto, but a piece that treats the organ as a member of the orchestra.
Asked about the challenges of playing the piece, DuBois gave a witty musician's reply. "Counting all the rests." In other words, knowing when to come in next.
But for the player, it has rewards. "What I like, toward the end of first movement, is the way the organ gives harmonic underpinning. In the last movement, it is the big chords at the end, and the way it revs things up and helps propel the music forward."
He says most instrumentalists are fortunate because they carry their own instrument with them when they travel. Organists don't have that luxury, so every time they play on the road, they have to adjust to the qualities of a different instrument.
For the Charleston concert, DuBois said he will be playing an electronic instrument built by the Allen Co. "It will have a lot of speakers for the sound."
His process to adapt to an instrument is a progression. "I do a rough approximation; it will take several hours. Then I will come back to it later to refine it. When I finally get with the orchestra, I will make more refinements as we go along.
"Organs are very different from instrument to instrument and hall to hall. You have to keep making adjustments."
The concert, the last in the 2012-13 symphonic season, also includes Bartok's Suite from the "Miraculous Mandarin," one of the great early 20th-century masterworks. Maestro Grant Cooper will lead "Preludes," a conversation on the concert's music, at 7 p.m. both nights.