Production Paths: Microphone Multiplication Part I

We could make a joke about today’s topic. How many microphones does it take to capture the sound of a symphony orchestra? The punch line might go something like this: Just one if you put it in the right place! But seriously, this is a question that every audio engineer has to answer when they approach a new recording project. It’s a tough one. And it turns out that there are as many answers as there are audio engineers working with symphony orchestras. There is no correct answer.

I’m back to the thread about recording production paths. I’d like to explore the “everyone is in the room at the same time” choice that I started with a couple of days ago a little further. As I stated two days ago, this technique is usually reserved for classical or jazz projects (although as regular readers will know…AIX Records employs this technique with all genres of music!). The reason is that the ensemble is well rehearsed and ready at the time of the session to “lay down” the music tracks. As we’ll see in a future post, most commercial recordings are not done this way. We need to be thinking more about a “sonic documentary” than a highly crafted original tune that is assembled over many sessions…the multitrack way.

The analogy to a documentary film is actually pretty well suited. You might think that a documentary filmmaker just walks around with a camera and a pole with a microphone on the end of it and captures glimpses of real life. It’s true that there’s no sets, props, lights or director saying, “Roll Sound…followed by Action!” But that doesn’t mean that the filmmaker is actually capturing real life unaltered and unfiltered. Documentary film making reflects the sensibility of the people making the film as much as the sound of recording session is the result of the choices made by the engineers and producers. There is no real life in docs or live recordings.

I was listening to NPR this morning following my Saturday morning run. There was a piece about a Swedish musician/singer that has chosen church organs as her primary instrument. This is not the usual singer songwriter choice and I imagine that it puts some serious limits on her ability to perform in clubs on “open mic” night. Anyway, Scott Simon did a nice interview with her and asked about the organ thing as you would expect. And of course, they played a few musical selections from her new album. The sound was bad but not to my taste at all!

A church organ can occupy a very large space to state the obvious. They are also located in large architectural spaces with lots of ambient reverberation…the church or cathedral. So as you might expect, the intimacy and focus of the sound of this woman singing was missing. The engineers that recorded the album made choices about which mikes to use and more importantly how many to use and where to put them.

My sense is they hung a stereo pair in the rafters not too far from the ranks of pipes to capture the sound of the organ, put a few near the percussionist/drummer and finally, put a mike in front of the vocalist. The resulting sound was similar to the sound that you would hear from the audience I suppose. It was distant, hollow, diffuse and too open sounding. But because this project must be recorded in the church, there really aren’t many good solutions available to the producer and engineer.

Back to the central question then, how many microphones is optimal for a live recording of a classical or jazz ensemble? The traditional answer follows the “less it more” doctrine. Throughout the history of recording, the number of available tracks that can be recorded simultaneously has steadily grown. Recordings from the 20s through the 50s were generally monophonic…captured to a single track or carved in a single undulating grooving spiraling inward on a wax or lacquer blank.

Then Blumlein and others moved to “stereo” miking and two tracks were recorded. There were actually wax/lacquer recording lathes that would cut two grooves at the same time! As soon as analog tape became the recording medium or choice in the 50s, the quest for more tracks has been unstoppable. Les Paul invented “ping ponging” and multitrack recording so that he could add multiple harmonic layers of Mary Ford and himself in his productions. In the 60s, there were 4-track machines (Sgt Pepper was done on only 4-tracks!), then 8-tracks, then 16 and eventually the recording industry settled on 2″ 24-track machines.

Today’s digital audio workstations routinely have many dozens of tracks and it’s not uncommon for a film dub to involve hundreds of tracks of dialog, music and sound effects. So unlike the “golden days” of classical recording in the 50s and 60s when engineers only had a few tracks available, now there are no limits.

Most classical recordings are done with “minimal microphone technique”. The pure stereo crowd believes that a single pair of mikes is all that is required to capture a symphony. After all, the conductor only has two ears…so why should the recording engineer need more than two mikes. Occasionally, they use “spot” mikes to focus in on a soloist or a specific section of the ensemble. And there are techniques like the “Decca tree” that use multiple mikes. All of these techniques place the microphones reasonably far away from the artists. The idea is to match the sound that reaches a member of the audience.

However, recording a large symphonic orchestra playing the cues for a blockbuster moves is completely different than a typical classical session. We’ll take a look at that in Part II tomorrow.