Ask any number of experienced gigging and touring indie acts for advice about playing live shows and you’ll hear one common refrain: Don’t piss off the sound person. Outside of your playing and singing abilities, the sound person is the only one who can make you sound good in a live environment. More than any other club employee — even the bartender sliding you free drinks — the sound person is the one you want on your side, the one you want for a new best friend, the one YOU need to be sliding free drinks to.

What’s the number one way to piss off the sound person? Missing or arriving late for the sound check. The sound crew arrives early to get the system set up and check the band. This means setting the levels and tweaking the audio to make your band’s sound and decibel level fit the club’s room. If you miss your sound check, you won’t get a chance to do it before the gig, because the doors have already opened and the crowd is settling in. This means you won’t sound your best no matter how well you play. But you probably won’t play your best, because you can’t hear yourself well in the mix coming through the monitors.

Barring unforeseen circumstances, such as a traffic accident on the way to the gig, missing a sound check is the height of unprofessional-ism. If you want to be taken seriously by club management and be invited back to perform in the future, little things like being on time go a long way. Even if you didn’t draw the biggest crowd, if you act like a professional you’ll be treated like one by the venue. If you act like you’re too cool for sound checks, you’ll come off like a jerk and not only will you not be invited back to that club, word will spread that you’re not an act to be taken seriously.

Furthermore, many sound guys have ways of dealing with bands who miss their sound checks. Though they’ll never admit it publicly, there’s a secret button on all audio mixing boards. It’s called the “suck” button. Miss a sound check for no good reason and your band becomes a prime candidate for receiving the suck button treatment, where with one push of a button or pull of a lever, your band’s sound sucks worse than it already did because you missed the sound check. Not only that, but every request for a little more guitar in the monitor will promptly be ignored, even when the guy behind the board gives you a nod and the thumbs up sign, before doing absolutely nothing. Trust us, it happens all the time.

So, don’t miss your sound check unless you have a note from your doctor, a huge dent in your van, simply like being unprofessional or enjoy sounding awful when you play in front of people.