Hey there, Michael, The first majour difference betwixt active and passive volume pedals will be the active pedals all use some form of power supply in order to add a bit of amplification to the line level, whereas a passive volume pedal won't. A better analogy would be a passive volume pedal would act more like the volume control on your guitar, whereas the active would be a little bit more like the volume control on your pre-amp. I understand that this isn't totally 100% on the ball as far as how they work internally, but this is just the quick explanation for it. Personally, I prefer the passive volume controls and use one both at the begainning of the effects loop and at the end (should I have the spare). This has more to do with using line level effects in my effects loop and also because I'd rather not deal with something loosing it's battery on me during a gig... Been there once and didn't have a spare... As far as I can tell you there are a few differences betwixt a volume pedal and an expression pedal, mostly having to do with one is a mono or pair of mono inputs, and the other is going to be at least a single stereo 1/4" and maybe some mono inputs, too. The latter pedal will control more than just the overall volume of an effect or keyboard, and really matters upon pre-programming and effects/voices being run. Typically, I tend to set mine to velocities and frequencies of the voice. Just makes things easier from a playing stand point. Your last question, I really can't answer off the top of my head, ... typically I'm the only one on stage, and I tend to use the tuner that is in either my Zoom 2100 or a Korg DT-1... Now that I have a GR-30, I'll probably be using it instead. One thing you may want to look for in a tuner is something that is rack mountable and bypassible. Hope this helps out. Tchus, Lee-ohki.