"Not necessarily, a lot of my songs are firmly tongue in cheek"

This quote by David Coverdale recommends that his songs are not constantly indicated to be taken seriously. He implies that some of his tunes are suggested to be amusing and lighthearted, and should not be taken too seriously. This might be translated as a method of expressing his creativity and having a good time with his music. He might be trying to communicate that his tunes are not always suggested to be taken actually, and that he is not constantly attempting to make a serious declaration. He might also be recommending that his tunes are meant to be delighted in and valued for their entertainment worth, rather than for any much deeper meaning. Ultimately, this quote by David Coverdale recommends that his tunes need to be taken pleasure in for what they are, and not taken too seriously.