I've been attending some friend's concerts and using my phone or my DSLR or my high end point and shoot the audio quality is extremely poor. I assume if I wanted the best quality I'd need to plug in directly to the amps / mixer for all the performers but I'm not doing this as a pro. I just want to be able to record a few 30 to 120 second clips and later post them on facebook / youtube. BUT, the audio at the events is extremely loud (I usually wear ear plugs) and on top of that it often sounds off key even though it didn't sound so off key live.
Is there certain easily portable equipment I can say add to my camera (a certain type of mic or mic + amp) that would let me record and get reasonable audio quality (for some definition of reasonable)? Are there special kind of mics specifically for loud situations or mic attachments? Do I need my own equalizer on the input or can I adjust the audio later in something like Audacity (or some more professional software). For example I noticed in one video the singer's voice seems louder than everything else but at the actual performance the instruments seemed louder than the vocals.
Note: I specifically listed a rock performance because they tend to be much louder than say a jazz performance. Also have friends in an industrial band and they are so loud I have no idea what they sing (haha). I just put my ear plugs in and enjoy the spectacle but I'd love to be able to record them too just as a member of the audience, not someone who has access to the stage (too much work and coordination, especially since usually many bands are playing). These are small venues that usually hold less than 50 people and usually each performer or band only does 3-6 songs and then the next group is on.
I want to make it clear I'm not trying to record concerts it would be illegal to record. Besides, my experience is those types of concerts confiscate all high end equipment on the way in. At least that's my experience. Example, you can take your smartphone in but you can't take your DSLR and I'm sure they'd check for mics etc. The places I'm talking about are small venues where I'm a friend of the band hanging out and taking pictures for fun etc. Here's a picture from last March 25th 2017 if you want some idea of the type of venue. That's literally 1/4 of the venue. Another 1/4 is the bar leaving space for about 15 viewers.