http://www.cupofwonder.com/secrets.html Focus on the fine indeterminate line where the sky meets the sea. Desperate midweek words, banal and absurd freely flow out of me. Oh, I may be a hostage to summer but I'm a hostage, not a slave. And I'm clear that I wish you were here on this postcard day.
If you look at the start of the song he is doing some work, adding up numbers or something, so maybe it means: Here am I stuck in an office working, trapped in a situation away from summer and all of its joys. But being a hostage doesn't mean that I can't stop work and think about what I am missing out on, including his lover, because he is a hostage but not a slave, i.e. compelled to work against his will.
Just a really wuick think about this - could be wrong. It has been known to happen ;->