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The Milwaukee Symphony Orchestra, which last June became one of the first orchestras in the US to launch its own e-label, has now become the first orchestra to offer download-only binaural recordings. The binaural process, whose benefits are most apparent to those who listen through headphones, is based on the concept that the best way to reproduce the concert experience is to make sure that the recorded sounds that go into the listener's ears are as close as possible to what would be heard during an actual concert.

The MSO's binaural venture is the brainchild of Robert Levine, cochair of the orchestra's Internet Oversight Committee. Levine also serves as the orchestra's principal violist, as President of the local chapter of the musicians' union, and was just appointed to the Board of the American Symphony Orchestra League. He is thus in a unique position to negotiate agreements between musicians and management, and to advance experimental projects like this within the classical community.

Levine describes the binaural process: "Ears are not just biological microphones; they are microphones embedded in the complex structure of the human head. Sound waves that arrive at the eardrum are modified dramatically by the shape of the head and even the shape of the ears. The brain localizes sound by using those modifications, or 'head transfer functions.' "

Unlike "normal" stereo recording, binaural recording uses only two microphones, each embedded in one of the ear canals of a dummy head (aka "the head'). When binaurally recorded sounds are played back directly into the ears via headphones, the listener often feels situated exactly where the head was located in the concert hall during recording. If the head is positioned optimally—eg, on the edge of the stage, where there is minimal blurring from hall reflections—the listener will ideally experience the benefits of that position's clarity and ambience.

"This makes the listener feel as if they're in the best seat in the house," Levine claims. "It also allows the listener to hear the composers' orchestrations in a new way. Musical lines that are compressed together in other recordings become distinct in binaural. The listener can hear, for example, that the first violins are both to the left of and in front of the second violins; such precise localization brings to life contrapuntal writing in a way that's impossible to fully achieve with conventional stereo. Simply put, the listener can hear aspects of music in a binaural recording that they have never heard before."

MSO's goal is to make 10 to 12 new binaural downloads available for sale each year. Their first such offering, Saint-Saëns' Symphony 3, was recorded very close to the stage, during the initial experimentation process. Tchaikovsky's Symphony 5 will be up in March, and in April, Grieg's first suite from Peer Gynt (conducted by Vasily Petrenko in what may have been his US debut).

"What I most enjoy about a binaural recording is the sense of physical presence," says Levine. "To me, it sounds more like a performance than anything else I've heard, although that may be in part because it sounds more like my normal on-stage experience of a performance than normal recordings provide."

A free, unedited, sample download, of the second-movement Andante of Tchaikovsky's Symphony 5, is available at www.milwaukeesymphony.org/media/mp3/tchai_5_2.mp3. Like all MSO downloads, it is encoded at 320kbs, which the highest rate short of lossless available in AAC or MP3. While the MSO has considered going the lossless route, or even producing SACDs, Levine notes that he hears "very little difference" between CDs and MP3s, perhaps "because of my damaged hearing after 30 years playing in an orchestra." (Now there's a comforting thought. Imagine being able to hear more from a binaural recording than a seasoned conductor might hear standing in front of a full orchestra.)

Levine has been a self-described "headphone nut" since high school, when he owned a pair of Koss Pro4As. Aware of the binaural process early on, he realized, soon after the MSO took the download route, that the sharp increase in iPod headphone use had made binaural downloads economically viable. Levine presented the idea to the MSO's recording engineer, Hudson Fair, who engineered the recent, Grammy-winning recording of the late Lorraine Hunt Lieberson's interpretation of the exquisite Rilke Songs, by her husband, Peter Lieberson. Fair in turn contacted Full Compass Systems, a professional audio/video mail-order retailer whose founder, Jonathan Lipp, has created a virtual museum collection of Neumann microphones, to see if he could borrow one of the few Neumann binaural microphones available.

Using the Neumann mike, last November the MSO recorded Carl Orff's Carmina Burana. After an additional experiment, the results proved so satisfying that they the orchestra raised funds to buy Neumann's latest binaural mike, the KU 100 (aka "the head"), in May 2006. Very few KU 100s have been manufactured, and none was in inventory in the US when the MSO placed their order. Since receiving it, however, the orchestra has recorded all of their subscription concerts with "the head." Hudson Fair records at 24-bit/96kHz, using a Crookwood PaintPot mike preamp into a Tascam DV-RA1000 digital recorder.

"One of the things that is very attractive about this technology is how easy it is to record," says Levine. "You find a location that works and you use a single binaural mike. There's no mixing, no tweaking. The process has led us to rethink microphone placement. For stereo recordings in our hall, we favor hanging microphones directly over conductor Andreas Delf's head. But for binaural, we hang the head 11' up, 11' or 12' in front of the conductor. While we're very happy with the results, we still have some experimentation to do.

"There's no such thing as 'accurate sound'," Levine continues. "It depends so much on how it's recorded. If we move the head up or down 2" or 3", or back and forth a foot or so, it really changes the sound. So we go for what we like. I've been listening on Grado headphones and high-end AKGs. They sound different, but which one is right? We seat the head at the edge of the stage, where the sound is much better than farther back. When we record normal stereo in our hall, we cover some of the seats with plywood for added reverberation. [Telarc does the same when it records the Atlanta Symphony Orchestra.—JVS] When we keep the mike head within the shell, the sound is quite good."