Maybe more than you wanted to know, but... the backing tracks are wav files (technically a high quality AAC file) that I produce in Logic. These are covers, so often I'll try to find some commercial MIDI version for a jump start, then voice and customize from there, or start from scratch if not available. The
BandHelper app (fantastic for this purpose) runs on an iPad and on launching a song it generates the following synchronized output:
1. The backing track audio file
2. An accompanying MIDI file to control lights (which I also create in Logic)
3. What BandHelper calls 'Automation', which is their own facility for managing synchronized MIDI... that's what I use for guitar patches, fx, vox reverb changes, etc... a little easier to tweak there than in Logic.
4. Scrolling lyrics and cheat sheet stuff for my crappy memory ;-) (Its display is also simulcast wirelessly to the other performer's iPad)
The iPad connects via lightning to an iConnectivity Audio2+ which acts as a D/A for the backing track before it gets sent to FOH, as well as a MIDI interface to all the downstream effects, lights, etc.
It's a lot of work preparing each song, but when performing* it all works and we just play! I like having presets magically change while playing without messing with pedals.
* which I hope will happen again Some Day!