Audio Source Scanning

Perfecting Your Live Audio Mixing Skills

Source Scanning ~ a Technique Borrowed From Aviation
~ by Ethan Harris ~

When training for my pilot license and instrument rating years ago, my flight instructors continually hammered away at the critical need to continually scan the cockpit flight instruments.

They told me my life depended on it. They demanded I understand what the flight instruments were indicating and what to do in response. They told me that this would save lives if things went bad in flight.

My instructors were right. No one wants to be a smoking hole in the ground.

As part of flight training you learn to continually “scan” all the flight instruments in a specific sequence looking for any anomaly that might suggest the aircraft’s airspeed, heading, altitude or attitude (pitch, roll, yaw) needs adjustment. Pilots are trained to make small corrections quickly and early before small problems grow and become a threat to life and safety. The instruments tell you the health of the aircraft, and crosschecking the instruments can even tell you if a particular instrument is failing and should not be trusted. These are all critical things to know when you are the pilot-in-command and you own the responsibility of keeping yourself and your passengers safe.

Misreading flight instruments often has serious and sometimes fatal consequences. Because of this, aviation has a clearly defined set of rules and procedures. As a church tech I have learned to apply some of the ideas and concepts of these types of flight procedures to my work behind the mixer ~ and with great results.

I have observed dozens FOH engineers at work during rehearsals and worship services. I have noted a fairly common tendency where some audio engineers seem prone to fixating, and applying way too much attention on a particular fader strip as they work on the mix. They continually make adjustments to the person or instrument they are focused on. Unfortunately, on occasion the rest of the mix goes flying (excuse the pun) out of control, resulting in a crash and burn mix.

I have done this too ~ so don’t feel bad. On one occasion, after the Monday morning post-mortem of a worship service mix that was not my best, I decided to apply the “scanning” discipline I learned in flight training to my work behind the mixer. I was surprised and blessed by the results and the improvement in the sound of my mixes.

So what does this mean?

I call it “source scanning.” With source scanning you train your ears to listen to each and every vocal and instrument source, one source at a time, and in a specific sequence, but only listening to that source momentarily. The objective is to consider how each source sounds in the mix, make a quick correction as needed, and immediately move on to the next audio source. The idea is to scan every source of audio quickly and repeatedly, over and over and over, such that nothing gets out of hand.

In aviation, it’s easier to tilt the wing slightly for a split second to bring the aircraft back to stable level flight than it is to get an out-of-control aircraft back to level flight from an inverted stall. In live mixing terms the process is to listen, tweak, and move on to the next source in your scan pattern.

Set up a specific pattern for your scan. Know ahead of time the order in which you will scan your audio sources. Sometimes you might scan all of the audio sources in sequence, and continue to scan the list in the same order over and over. At other times you might decide to scan a “habitual problem” source more frequently, such as a vocalist with poor mic handling technique. In this sort of situation, scan the problem source, then scan a few other sources, and then go back and scan the habitual problem source again. Then scan several other sources and then pop back to the habitual problem source, etc., until you have made a complete scan of all the sources in your mix.

You get the idea. The order of scanning is arbitrary but here are some suggestions: I find it helpful to scan the lead vocal first. Then the lead instrument. Choose the order of scanning that is appropriate to your situation. The key is to stick to it, and never stop scanning. As you get used to scanning your audio sources, you will find yourself scanning all of them more quickly. This means you will begin hearing things early, and reacting to small things in the mix far faster ~ for a better sounding live mix. But be careful you don’t overreact to small stuff and tweak before it becomes necessary.

How fast can you scan? With practice ~ really fast. I practice scanning all the time when listening to music in the car, in my office and elsewhere. It quickly becomes second nature, and it’s almost as if you are paying attention to each and every audio source simultaneously. With a half dozen vocal sources and a typical contemporary praise and worship band, I can scan all of the sources several times a second.

As you get good at it, your scan of each audio source will include the volume level, the EQ, compression, reverb, and all other aspects that contribute to the sound of each source. You can even include a peek at the upcoming audio cue list in your scan. That way you can anticipate and be prepared for what is coming next.

For those who mix FOH and also use sends-on-faders to control a mix to the live stream at the same time, simply bank to the aux and listen to it on headphones as part of the scan and loop through all of the sources going into the aux. Then bank back to the main. I usually rescan a stream mix less frequently, usually at the transitions between verses, choruses, bridges, etc., as soon as I have settled the FOH mix.

With “Source Scanning” you will find yourself identifying and making live mix adjustments quickly, and all of the aspects of your live mix will sound better. So buckle up and ~ And have a safe flight!

Ethan Harris is an accomplished top-10 market technical director with decades of pro-audio, acoustics, lighting, video, and high-tech management experience. He can be contacted at

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