I noticed this today! I have always been under the impression the bridge pickup is what you should tune with. I may keep doing that, but read on, this is weird!
Warmoth superstrat bridge pickup = spot on
Warmoth superstrat neck pickup = slightly down
Barrington HSS superstrat bridge humbucker = spot on
Barrington HSS superstrat neck singlecoil = slightly down (but not as much as the other guitars)
Musicmaster with bridge pickup = spot on
Musicmaster with neck pickup = slightly down
Musicmaster with piezo saddles = slightly down
And I dont have any pickups that are right under the strings (except EMGs which are designed for it) pulling them downwards, but then again, that should be affecting both pickups, right? aaaaaaaaaah
So, my experiment shows that the PIEZO SADDLES should be the most reliable, since the strings go DIRECTLY into the tuner?
If so, is bridge pickup a BAD THING to tune with???
Have we all done it wrong all the time?
Now of course, I use a neck pickup maybe 20% of my soloing, so I guess I'm fine with tuning with the bridge pickup and then having the neck soloing being slightly off, because I have never really noticed that while playing. But now I maybe have must be more careful!
Does somebody have the same experience?
This is pictures tuning my Warmoth superstrat!
The pictures are taken RIGHT AFTER EACH OTHER and you can actually go back and foruth between the neck and bridge pickup and you will get the pitch higher and lower each time!
it's almost like it picks up different sections of a vibrating string