"Alla breve" music function

[Markus Schneider]

Hello list,

I'm looking for a function that doubles every duration.

Here's a short example:

Turn { c1      c2 c4 c16 c16 c16 c16 }
into { c1 ~ c1 c1 c2 c8  c8  c8  c8  }

I digged around, but I think this is still beyond my limited scheme
understanding.
If someone did somthing like this already or can give me a hint, I'd be
happy!

Cheers,
Markus