I know that a Christian can listen to secular music cz jesus says what goes inside, doesn't defile you. And paul says that eating meat at the temples of unbelivers is not a sin. So not only these verses go with food but everything. But what if a Christian wants to sing secular music? Not the one which goes against the law of god, for example , which has profane lyrics and promotes adultary, homosexuality , drug abuse and all that. But the one which is good but not explicitly Christian.