A thorough look into adding a phantom member to your band for a solid live performance.
A client of mine recently lost their rhythm guitarist and asked me how to add a simple backing track to their live show until they could find a suitable replacement. This is similar to the setup I used live for FX and ambient guitar leads when we were only a four piece. The only potential problem I foresee is turning a mono signal into stereo for the drummer so it plays out of both in-ear-monitors. In that case, you can purchase a mono to stereo adapter off amazon for $4.
WHAT YOU NEED
This is the simplest and possibly the cheapest backing track setup possible meant to keep everyone on time and provide the front of house with a single prerecorded rhythm guitar track. The only extravagance is providing the sound guy with a 25' XLR cable to go from the adapter to the stage snake. He probably won't need it. The stage snake, mixing board, and drums do not need to be purchased; they are just for visual reference. Your playback device can be anything you want with a 1/8" stereo output. (MP3 player, phone, tablet, laptop...) I would NOT rely on Dropbox for your files, just download them straight to your playback device and remember to always keep it charged up. I used an old iPhone 4 I had lying around because it was free, it had an 1/8" stereo output, and it was reliable. I do not recommend using your personal phone and Bluetooth in-ear monitors. I do suggest a decent set of in-ear monitors specifically designed for drummers that block out ambient noise so you don't have to crank the volume level.
PREPARING YOUR AUDIO TRACKS
Whether you prefer a single stereo WAV file for each song or a single stereo WAV file for the entire performance is up to you. Just remember that you will need to record and prep the playback tracks yourself. I don't recommend hiring this job out to an audio engineer so you can remain flexible and make changes to your own tracks as the need arises. You will need to design the set list, playback audio, and performance in such a way that everyone follows the drummer and the drummer is keeping time no matter what. This includes counting in all songs and keeping tempo throughout any breaks or pauses in the songs. As a drummer, I liked a two bar click track of 1/2 notes followed by two more bars of 1/4 note click track overlaid with ½ note hi hats for me to mimic and count the band into the song. Now let's assemble our tracks.
PANNED 100% LEFT
This will include anything you want to send to the front of house to be played through the PA. This setup is intended for a single prerecorded rhythm guitar track but you could expand this idea to include intros, FX, ambient guitars, or even backing vocals if you wanted. Just be sure that the only things panned left are elements that you want sent out to the PA and therefore the audience. You wouldn't want the audience to hear your click track. And don't forget to make this track as loud as possible to give your sound guy enough level to make it work.
PANNED 100% RIGHT
This can be whatever your drummer wants in his in-ear monitors. My personal preference is a loud 1/4 note click track (including a long count in for each song) overlaid with the original album audio. But maybe your drummer just wants a click and the prerecorded rhythm guitar track along with prerecorded vocals. Every drummer is different. Some drummers even like a vocal overlay announcing parts, songs, tempo changes...
PRACTICE PRACTICE PRACTICE
Don't forget to practice setting up the rig, troubleshooting, playing along with the track as a full band, and even practicing without it just in case the rig fails you for some unforeseen reason. This way of performing can take a little getting used to but you'll find that your live performance has never sounded tighter. That's it, it's that simple. Depending on what you may already own, and your ability to assemble your own tracks, this backing track rig can be assembled for less than $100. Have fun.