Long fingernails are NOT good for a guitarist. You can't push the strings down properly with them long. As for keyboard.. same thing (Not to mention you may break a nail if you end up playing like Tori Amos (BANG !! BANG !! BANG!!!). Cut them down as short as you can get them for optimal control of your instrument (Or if you're in one of those freaky bands and wanna try for a really wierd look, have them removed altogether Hehehe !)