This is absolute sacrilege. If one of your friends played the clarinet, you wouldn't nab it from them and blow into it willy-nilly, sticking your fingers over all the keys and making a truly awful noise. At least with a clarinet youd be punished by being covered in your friends spit that's stuck in the reed. People who "want a go" on someone else's guitar and then strum as hard as they can putting their fingers in random places are the worst. Asking for a lesson is better, but teaching people things is hard and the guitar is no exception. Theres a reason why teachers have qualifications, and its because most people dont have the patience to be nice and help as you massacre a simple A chord. Sometimes its fun to teach someone an easy and recognisable riff if weve offered and youve bought us a drink, but most of the time its torture and we have no idea how you're making the guitar make that horrible noise.
