Sound Engineer Mixing Audio Tracks

Tech Tip: Gigging with Mobile Devices: Make Those Backing Tracks Mono, Part 2

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Why you want to mix your backing tracks in mono and how to do it right

If you’re going to accompany yourself with backing tracks played back on an iOS device, laptop or MP3 player there are some compelling reasons to mix those tracks in mono. While we appreciate the time you’ve spent mixing and panning your sounds in stereo, your audiences won’t. Especially the ones near the right speaker who can’t hear all the cool stuff coming out of the left and vice versa.

Live performance is best done in mono so everyone gets to hear your tracks in their full glory regardless of where they are in the room. So, first and foremost, create your backing tracks in mono. That way, you know your mix works. If you plan on using stereo tracks, you need to be sure that your stereo mix works in mono. Just combining the two channels and squeezing them into one cable won’t do it. In fact, if you read the previous tech tip on connecting an iOS devices and laptops to a mixer, you know that combining your stereo outputs to mono with a "Y" cord can result in severe signal loss and possible serious gear damage.

The Problems

Without going into too much technical detail, there are three things that are affected when stereo tracks combine to mono; level, timbre, and ambience. Interestingly enough, though differences in arrival time to our ears from two sources allow us to localize sound, when those two sources are combined in mono, sound quality changes. For example, when a dry guitar and its delayed signal are panned apart, the difference in propagation time between them places them in a certain location in the stereo field. When those two tracks are combined we lose spatial information, and the differences in propagation time now affect timbre. It’s an effect called comb filtering, and it can cause loss of levels, hollow- or gritty-sounding instruments, and bass to drop out. You may also hear a loss of spaciousness and reverberance. The solution is to mix your backing tracks in mono from the get-go.

Tips for mixing in mono

Record in mono keeping your tracks center panned. Don’t record a stereo keyboard on two mono channels. Record keyboards on one channel. Most, if not all keyboards have a mono output (usually the Left out). Use it. Most stereo patches on synths and keyboards are not true stereo anyway and tend to do funny things combined in mono.

Avoid excessive use of reverbs and delays. You’ll have plenty of ambience in the room you’re playing in, and the dry tracks will give your live instrument a nice contrast. If reverb is a part of the sound you’re recording, such as a snare with gated reverb combined with a small hall reverb, and a plate reverb; record with the effect and treat it as part of the sound of the instrument. Since you’re already working in mono, there’ll be no surprises…well, maybe one: If you don’t print the reverb and save it for later in the mix, you may find that its space has been taken over by other instruments and overdubs.

The first thing you’ll notice as everything piles into the center spot is that EQing sounds will become very important. Stuff will turn to mud real quick. We’ll talk more about that later, but for now, since reverb is fresh in your mind, set up your reverbs with a fast low-end decay, and EQ the reverb itself, rolling off the lows. This will add transparency to your mix and avoid the muddy "coming-from-the-bottom-of-a-well" sound—and not a clean well either.

Reverbs and delays can help to bring a sound forward or backward in a mix, but without the stereo field, that can contribute to mud quicker than clarity. Another thing to consider is that your backing tracks will be creating the illusion of a band onstage with you. Most bands set up in a very linear fashion. Most importantly, the cleaner your backing tracks, the less that can sonically go wrong when you encounter the unpredictable ambience and acoustic behaviors of a club.

If you have original songs that you’re recording in stereo, create a mono mix from them. Select the parts that are most essential to convey the song while leaving the focus on your performance. They are backing tracks after all, and you might want to give people a reason to buy your CD and hear the full arrangements. If you’ve recorded tracks in stereo, listen to both sides, pick the one that sounds best and throw out the other. Guitars that have been recorded with delays or reverbs that have been panned opposite the source are a common source of stereo cancellation in mono. Lose the delay/reverb track and keep the dry, unaffected signal.

Build your mix from the bottom up. Start with kick and bass. Once you have those two sounds working together, make sure their combined levels is between –5 and –7dBVU. That should leave you with enough headroom for the other instruments. You may be able to go a little hotter if your arrangements are fairly sparse. Now, add in the rest of your drums and other percussion instruments. Next would be your rhythm instruments such as guitars and keyboard pads.

EQing for mono

As we mentioned earlier, you’re biggest battle is going to be EQ. (Okay, we didn’t say that specifically, but it’s still true.) As instruments start to pile on, overlapping frequencies are going to make mud. To EQ in mono, always cut a frequency before you boost. It helps if you think of your mix like a totem pole: a continuous sculpture of heads where the top of one is the bottom of another, yet each has a distinctive face.

In mixing, suggesting a sound works far better than trying to jam the full spectrum into the mix. For example, take an acoustic guitar and roll off the EQ dramatically below 325Hz. It doesn’t sound all that great by itself, but when you drop it into a mix with other electric guitars and bass, it will sound fine. Your ear will add in the lost frequencies.

Starting with the low frequencies, lower bass is between 40-80Hz, upper bass is between 80-160Hz. Musically speaking, that’s the second and third octave. Keep these reserved for kick and bass, and roll off anything that gets in their way. From 160Hz to 1.25kHz is where things can get punchy and powerful, not to mention darker and muddy. Don’t be afraid to cut frequencies here. Musically, this would be octaves four through six.

From 640Hz to 2.5kHz, you’ll find that keyboards such as electric pianos have a lot going on there. Guitars also share that space (and down to 100Hz as well) so divide your sonic real estate between them. Musically, this range is octaves six and seven. Again, don’t be afraid to roll off the lower frequencies. The next octave, number eight, which is from 2.5kHz to 5kHz, is a very important one. Keep this reserved for voice. This will be very important when you try to sing against your tracks. If you’ve boosted in this range, it may sound fine in the mix, but you will experience conflicts when you try to sing.

Octave nine, 5kHz to 10kHz, is where you’ll find sounds such as the metallic picking sound of acoustic guitar strings and attack information. In fact, the kick drum has information in this area. As a side note, you can boost bass at around 900Hz to bring it out without overpowering the mix and your overall levels. Be careful, too much can make mud.

Finally, in octave ten, which is from 10kHz to 20kHz, you’ll find the hi-hat predominantly and not much else. This is where producers and engineers add extreme high-frequency content such as overtones and the ever-popular "air" to vocals. Keep this spectrum in mind, get to know it intimately, and make sure that your instruments share the range in peace and harmony, so to speak. Boost with care and don’t be afraid to cut lows. It’s very important to manage your low end.

If you boost two instruments at the same frequency and both sound good individually, they will fight for space when combined. If both sounded good at 2Khz, then boost one at 1.5k and the other at 2.5k and see what happens. The same thing applies if you cut. For example, if you have four guitars, start with a different frequency for each. For example, guitar 1, roll off at 100Hz, guitar 2 at 115Hz, guitar 3 at 120Hz, etc. Since you won’t have the depth of stereo, all of your instruments are going to sit on top of one another vertically.

Parting shots

While it may be tempting to back yourself with a virtual London Philharmonic, it will seem a bit odd to your audience, particularly if you’re a solo performer. Keep track count relatively low. A basic rhythm section will do nicely, plus you can add the occasional instrumental synth hook for authenticity (if you’re doing covers). Remember, the trick here is to add fullness to your performance, not look like a karaoke singer. Plan your backing tracks as though a three- to five-piece band were playing them.

Or, you can go overboard if you like, but we can tell you from experience, with overdone backing tracks, your audience will begin to wonder if you’re actually playing or just faking it. Remember, in live performance, nobody is giving you credit for all the tracks you sat at home and programmed. They can stay home and listen to CDs if they want. When they go to hear live music, it’s live music they want, and the more you can do live, the better. In short, let your backing tracks back you up, don’t let them become the whole show; people should focus on your performance.

When it comes to tracking and mixing down those backing tracks, you’ll find a huge assortment of recording gear at Musician’s Friend to help you sound your best.

Tags: Recording Mixers


# Breezy Flame 2016-02-25 18:37
i learned alot from this article about the frequency spectrum

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