So playback is a largely varying necessity for most artists. I’ve worked with bands that play to click tracks, I’ve worked with bands that are playing to click plus additional tracks, and I’ve worked with artists that are almost entirely on tracks. Some of these rigs are as simple as an iPod, some are dual Pro Tools HD rigs with racks of interfaces and DIs with auto switchers, and everything in between. A playback rig doesn’t need to be anything particularly complicated, it’s all really relative to the needs of the show. Currently the playback rig I’m dealing with right now is a pair of Macbook Pro 13s, a pair of Echo Layla interfaces, and a pair of Radial SW8 Switcher/DIs. While not a large playback rig, it’s quite capable and can run 12 separate outputs and has a backup playback system.
The necessity of your playback system is entirely relative to your show. If you don’t have your own sound team you might want to go simple, if you have your own crew that’s when you get to go all out and have an extensive rig. When you simply need click track to feed to a drummer, and a mono playback to run out to house, you CAN build the entire playback to feed left as click, and right as all of the playback. This can be played from an iPod, or from a computer if you need an interface that allows you to see more of what’s going on. The downsides to this method is that the tracks are in mono, they’re premixed, and can’t be changed by your FOH nor Monitor staff, there is no redundancy, and often there is a slight bleed between the left and right, which is often acceptable, but it can sometimes be a problem, it all depends on the situation. Even if you’re using a laptop for this, you CAN use the headphone output. It’s best to use a DI between the laptop and sound system (if you have any noise or buzz issues, the DI can often help), but it’s not ENTIRELY necessary.
In the case that you need more than just two outputs, this is where the rig expansion can get daunting. Once you’re upwards of two outputs, the situation requires using an external interface with your computer, or a self contained playback system. Usually an artist will start with something like Tracks L, Tracks R, and Click, which is just three outputs, but at least allows you to have stereo playback. Beyond that you can add outputs, and stem things out to allow your sound crew more control, such as Switcher Tone, Sub Bass, Percussion Left, RIght, Instruments Left, Right, Background Vocals Left, Right, Count In, Click Track, SMPTE Time Code, MIDI Controller Switching. An output setup like this lets your audio crew treat each output differently, and automate for different songs, as well as SMPTE Code will allow you to sync to video playback, and the MIDI outputs can either trigger lighting programs, guitar amp setting changes, pedal changes, or even FOH console scene changes. Another benefit for having a multiple output playback rig is the ability to have separate or different click tracks for different musicians, be it halftime, double-time, cowbell, or marimba… You can make a rig as complicated or as simple as you’d like.
Normally the setup for a system like this is a laptop with Ableton, Digital Performer, or Pro Tools with multiple tracks feeding multiple outputs from one interface. A second laptop with a duplicate of the session feeding the second interface. The two interfaces are patched into A and B inputs of the Radial SW8 or ASW8 (the auto switching version), and the outputs of that rack feed right into the sound system. When using a Radial Switching DI, the Switcher Tone is always set to input one, as the device uses that to sense when the A playback machine has failed. When the SW8 stops seeing tone from machine A the alarm goes off on the device, which indicates that it needs to be switched to the B inputs (via a simple pushbutton on the face of the unit). The ASW8 the Auto Switching version, automatically switches when the tone cuts.
Having both machines play simultaneously is an interesting task, I’ve been told many methods by many professional touring artists, some make sense, some make no sense to me at all, but they’re considered standards… What I would suggest is having a controller of sorts, be it a midi keyboard, or a midi output from an SPDS drum pad, and set one (or the left half of the keys) to trigger ‘play/stop,’ and another (or the right half of the keys) to trigger ‘next marker.’ If you’re doing this, you can simply put a piece of tape or adhesive foam across the keys so you can hit them with a drum stick if need be, and it will trigger whatever you’ve set it for. The play/stop command, is essentially the same as hitting space bar, so it toggles between play and stop depending on the current state of playback. The ‘next marker’ command is very easy to set up in Ableton, and Digital Performer, but in Pro Tools it’s a bit more complicated, in fact I can’t even remember how you do it right now, so I can’t even explain. More important than the controller itself is making sure that it feeds both your A and B playback machine, so that they start and stop simultaneously, if you’re on a Pro Tools setup, be sure to turn on the stopwatch icon in the transport window, this sets that as the slave machine such that it maintains timecode lock with the main machine (unless the main machine stops, in which case it keeps going).
One thing to be aware of when using laptops as a playback system, hard drives skip when they are shaken. If your computer is living on a stage that takes a lot of low end, be aware that you need to keep it from rattling or shaking. The simple solution is to keep some foam under the machine, or a sheet of rubber. The better solution is to take out the hard drives, and replace them with solid state drives. Since solid state drives have no moving parts, you no longer run the risk of skipping from low end, and they also happen to have a better data transfer rate than regular hard drives anyway, so all in all, it’s a win.
The scariest thing about having a complicated playback rig, is your true dependency upon it. The more there is in your playback rig, the less you can cover, if for some reason it fails. This is also why redundant systems are pretty much imperative for professional touring applications.