Organ lab

The audience sits quietly and expectantly in church pews holding smart phones rather than choir books. Not quite sure what to expect, they've come for an event billed as an interactive organ concert in which the Cologne Cathedral's massive organ is to be connected with a specially developed app.

The occasion is the Interactive Cologne digital conference, expanded with this musical experiment. Norbert Oberhaus, one of the organizers, is also behind the city's c/o pop music festival in late summer.

"We wanted to make this digital festival a bit more lively and tactile," Oberhaus said. "So we came up with the idea of bringing the internet economy and music together. It had to be something special, so we chose the Cologne Cathedral, which is of course just an unbelievably great building."

Experimentation is nothing new there, says head organist Winfried Bönig, "Of course, it's not the norm during a normal mass, but we do play experimental music at special events."

Hitting the keyboard

The first piece is randomly generated. Titled "Lux et Color," it musically parallels the stained glass window in the cathedral's west wing designed by Gerhard Richter. "The idea was to transform the Richter window with its more than 11,000 colored squares into music," Oberhaus explained.

Adding an additional dimension is what Winfried Bönig calls an "acoustic flickering," as audience members' cell phone displays light up. Even before the first note, the phones were flashing in turquoise, violet, yellow, blue and orange patterns, with the enormous Richter window as a backdrop.

Then, soft tones emanate from the pipes and dart past the listeners' heads like fleas - all 12 notes of the scale in arbitrary order. It builds to an acoustic flickering in every timbre and color the organ can produce: loud, soft, piercing, gentle, sometimes few, sometimes all of the keys at once. The ten-minute piece puts the venerable instrument through its paces. The music is certain not to appeal to everyone - consisting, as it does, of 11,000 various notes generated by a USB stick. The organist's job is to pull thet stops and control the registers and, as such, the overall sound contours - with impressive results.

And onward…

Then Cologne-based composer Gregor Schwellenbach gets a turn with his "Interactive Composition #1." Based on the IP addresses of the listeners' smart phones, it's a mix of composition and improvisation.

"I decided on the character of the music in advance," Schwellenbach says. "I determined that I would use a seven-tone scale, so I only draw on certain numbers of the IP addresses."

He uses the numbers to create loops, adding, "The IP addresses are the notes that I use, and the rest is spontaneous."

After the music begins, the cell phones light up once they've been accessed. It starts with just a few blinking screens, but by the end, more and more light up to fit the musical crescendo.

'Organs are digital'

Head organist Winfried Bönig then returns for a round of improvisation at the keys and pedals. With a digital interface, he can steer the 380 smart phones on hand. The organ sends color signals to the devices, which light up the cathedral in response.

Communication between the organ and computers is possible thanks to technology that has been around in music since 1982: a MIDI interface. With it, commands can be sent from the computer to the organ.

"The organ is better suited to this than other instruments," explained Gregor Schwellenbach. "With piano, it's all about how you play the keys. But with an organ, it's not the key that creates the sound, but the pipe. The keys just give information about which pipe is to be used. So it doesn't matter whether a person is playing the organ or a laptop."

Schwellenbach adds that he's often had to explain that organs are essentially digital instruments - without electricity and in use for centuries. Organ pipes, he explains, only know two commands: yes and no, one and zero. "As such, it's as if the MIDI system were made for the organ."

By the end, the mood in the audience is mixed. One attendee says the music isn't very impressive. "But technically, it's pretty crazy. You can't just sit down on a weekend and write software like that."

For his part, Gregor Schwellenbach is pleased, saying, "I'll probably never do such a technologically complex thing in my life, no matter what kinds of crazy compositions I come up with."

The technology functioned without a hitch - at least on the digital end. The Cologne Cathedral's organ had a hiccup ahead of the third act - the system required a "restart" of sorts.