I have a serious, artistic hobby and I write an application for a scientific job. The hobby is music. I studied music for three years, but didn't conclude, because I decided to pursue a scientific career. I kept playing horn1, however; since lately I play in a (non-student, serious) orchestra.
I've seen that professors add information of this kind to their, say, online CV's. But first, they probably do not apply for grants using that version of their CV. Secondly, they are already somehow "respected".
That hobby was an important part of my life, thus I'd feel somehow dishonest to exclude it from the CV. It also explains why I'm about two years older than an average PhD student is where I studied.
Is including an artistic hobby in my CV detrimental for my application?
 This is not really the instrument but just an example.