Question: I play electric guitar and today I had an experience where the guitar would give very slight tingling sensations - I wouldn't quite call any of them a bad shock because none of them really hurt badly, but it was noticeable.

My question is: how to I test if the outlet we use is grounded properly. My bassist who uses the same power strip also said he gets little shocks from his bass. We play at football games and we are on those metal bleachers doing pep band crap which requires us to use an extension cord that connects to a power strip - everything that is connected is three prong including the amps.

Is this a situation where it's dangerous enough that I shouldn't plug in again until I know the reason why and fix it?

Answer: 
YES, you should not plug in without testing the ground, and you really should be protected by a GFI when playing outdoors. It is dangerous because you could be shocked or even electrocuted by playing without a ground or with a faulty ground. The guitar player for The Yardbirds was killed this way, look it up.

You can test for ground with an inexpensive plug-in device you can buy at any hardware store.

[![enter image description here](https://i.stack.imgur.com/vzpO4.jpg)](https://i.stack.imgur.com/vzpO4.jpg)
You could test the ground. Sometimes grounds are deliberately disconnected for audio / video equipment to eliminate noise problems. (Obviously that is a bad way to fix noise problems!) 

There are other wiring faults that could cause this issue, and some of them you can't count on an inexpensive outlet tester to find. So don't assume you're safe if the little tester says you are. 

You can get outlet strips and other portable devices that have GFCI built in, they are reasonably priced, not hard to find, and they can help protect you in situations like this.