Most of us are fortunate to have two working ears. When they work together, we hear our world in stereo. From a purely scientific view, they can detect the direction a sound is coming from. So they're useful for locating sounds of danger - like when your pot of soup is about to boil over as you're dicing the potatoes. But they're also useful for pleasure - like listening to a great music recording with spatial depth.
The quest for a natural sounding stereo recording is almost as old as electronic sound itself. As I mentioned in this article, two-channel sound had its start in 1881 but was not really accessible to the masses. By the 1930s, Alan Blumlein at EMI had patented stereo records, film sound, and surround sound. As with most technology that's created in the lab, it's usually another decade or so before it hits the mainstream market. Stereo LPs landed in the record shops in the 1950s, and FM stereo radio rocked the late 60s.
But as enticing as these new stereo delights were, they were treats only cherished by audiophiles. AM radio was how most people heard music, albeit in mono, and it drove pop record sales until the 1970s. So it's not surprising that when records were mixed, the mono version got all the attention. The stereo version, if it even existed, was an afterthought. After all, mono sound coming from a box was normal. Most people hadn't even heard a stereo recording until the Eisenhower years (his ears sure stood out).
How was stereo being created back then? Most stereo records being released in the 50s were often organic. That is they were recorded with two microphones in front of the performers, usually in a concert hall or large studio. In the smaller studio, it was much easier to record straight to full-track mono because the musicians were not set up in a line like they would be on a concert stage. During studio sessions, two- and three-channel reel-to-reel recorders were sometimes used as back-ups. For instance, an engineer might place all vocals and leads on the left, and all rhythm instruments on the right. These back-ups were only there to remix the mono version if something went wrong.
In 1957, Blue Note Records wanted to start releasing studio-recorded albums in stereo. They couldn't go back in to their catalog of mono recordings and just magically make them stereo, so they had to think forward. Recording technology created challenges, however. Creating a stereo master and then dubbing that down to mono created several problems, mostly generation loss and excessive tape hiss. But legendary recording engineer Rudy Van Gelder, who recorded a wealth of their albums, came up with an efficient way to produce a stereo and mono mix at the same time.
In those days, the majority of mixing consoles that were stereo-capable only allowed the engineer to assign a channel to left, center, or right with a switch. Pan pots ("panaromic potentiometers" that were rotary knobs allowing a mono signal to be swept across the stereo field) weren't commonplace until the 1970s. So instruments got panned hard left, hard right, or smack down the middle.
During the tracking/mixing session, Van Gelder used two recording machines and monitored in mono (he only had one speaker in the control room). The primary recorder was full-track mono. On the second, a two-track, Van Gelder assigned instruments to either left, center, or right. Since mono was king, the engineer, producer, and musicians worked on perfecting the mono version. It's important to note that in this era, Van Gelder and other engineers were recording AND mixing the sessions down to final masters on the fly!
The positioning of instruments hard-left and hard-right is a little jolting to us today. This was the mono era, so this stereo mix that's odd to us now was novel then. It was new and different, and each instrument could be heard more discretely. But converting an entire audience to a new way of listening wasn't going to happen overnight. Even Van Gelder admits that little attention was given to the stereo field. After some experimentation, he settled on the following stereo assignment for a typical jazz quintet:
Left: trumpet < Center: bass, piano > Right: drums, sax
In the 60s, rock musicians like the Beach Boys, the Beatles, and Jimmy Hendrix started experimenting with manufactured stereo. Meanwhile, the transistor allowed mixing boards to shrink in size and the pan pot became commonplace. Engineers could now place or "fly" sounds throughout the stereo field more easily. They could create a stereoscape that was both natural and unreal. Now they were cooking with gas!
(and pan pots)