Every term, without fail, I get a few assignments handed in with all of a mixer’s solo buttons enabled. The usual problem seems go something like this, “I turned a solo button on and it muted all of the other channels on the mixer. I’m not sure what happened but in order to hear my mix again, I had to turn all of the solo buttons on.” As ridiculous as this might sound to a pro, it’s a common mistake for beginners. If you don’t know what the purpose of the solo button is, you’re not going to understand what’s going on when you press it. So, let’s clear this up once and for all.
At its core, the solo button on a mixer channel allows you to quickly audition a signal all by itself, or with a group of other solo enabled channels, without needing to mute all of the channels that you don’t want to hear. For example, if you see a signal on Channel 10 but you’re not sure what it is because you haven’t labeled that channel yet, press the channel’s solo button. Or, if you need to have a closer listen to the blend on a three-part vocal harmony, press the solo buttons on all three harmony channels and instantly mute all of the other tracks in your mix. Then, to return your mixer to its normal monitoring mode, turn off all the solo buttons. Pro mix engineers are constantly switching back and forth between listening to soloed signals and the whole mix as they’re working.
The obvious reason why you don’t want to leave mixer channels in solo mode is because you might have a channel muted somewhere on your mixer that’s supposed to be in your mix. It’s easy to hear if you’re missing something really obvious like a guitar or vocal part, but you might not so easily realize that you’re missing an aux effect return channel. For example, if you’ve soloed a bunch of tracks your reverb return channel might be muted, and, consequently, you’d be missing much of the depth and space in your mix that was being created by your reverb send effect.
At this juncture, it’s worth noting that there will be channels you never want muted when you press a solo button. For example, if you always want to hear a soloed track with its reverb send effect intact. Or, when you have a MIDI control track that always needs to be running in the background (such as a drum track or controller data). In these situations, you never want the tracks muted when you solo a mixer channel. So, to safeguard these tracks the best designed mixers have a function called solo-safe which allows you to disable the track mute action for those channels in solo-safe mode. For example, in Avid’s Pro Tools you press Command (Mac), or Control (PC) and click on a solo button to enable a channel’s solo-safe mode.
It’s also worth noting that there are several different types of solo modes, dependent on the level of mixer (hardware or software) that you’re using. Top of the line pro mixers may have three or four different solo modes that you can switch between, while a basic home studio mixer usually just has one set solo mode. The two most common modes that you need to understand are latching and canceling. They may have different names dependent on the mixer’s manufacturer, but they will always operate in the same basic fashion. On a mixer with latching solo the solo button stays on until you turn it off. You can keep pressing solo buttons and they will all stay on until you turn each one off. On a mixer with canceling solo pressing a solo button turns it on and pressing another solo button turns the last solo button off. Consequently, in canceling mode you can only have one channel soloed at a time unless you hold down a modifier key while pressing additional solo buttons (such as the Shift key in Pro Tools).
I wish every mixer had, at the very least, these two basic solo modes. However, more often than not most mixers only feature the latching solo mode. And, those mixers that do have both modes are usually set by default to latching. Though, I can’t help but think that having the default solo mode set, instead, to canceling would help beginners avoid a lot of confusion. This, and Mackie’s brilliant feature on their hardware mixers, the Rude Solo Light. It’s a big red indicator that lets you know whether you have a solo button engaged somewhere on your mixer. Indeed, novices and pros alike can use this feature because when a mixer contains a ton of channels and a solo button is accidentally left on somewhere on the mixer, especially on a channel that has little or no audio, trying to figure out where all of your sound went can leave even the best producer scratching his, or her, head while they search for the problem.