Scheme help for lyric align on vowel

[Carl D. Sorensen]

There's been a discussion on -user about getting lyrics aligned on vowels.
Kieren came up with a clever, but somewhat cumbersome, manual means of
accomplishing it.  I'm trying to convert that to an automatic, virtually
transparent means.

I've got it all worked out, I think, except for one challenge that may be a
show stopper.

I need to define a function (double x) that can work as follows.  I want

(map double '(1 2 3))

to return 

(1 1 2 2 3 3)


Can anybody help me figure out how to do this?  As far as I can see, it's
not possible.

Thanks,

Carl