Extract source code /with/ captions

[James Harkins <jamshark70@gmail.com>]

I'm working on a set of Beamer presentations with a bunch of source
code blocks. I would like to collect all the blocks into one text file
per presentation, but I also need the captions and ideally a numeric
index.

That is, I'm *not* looking for the normal behavior of
org-babel-tangle, which assembles only the source code itself without
any other identifying information (on the assumption that the tangled
file should be OK to be compiled). These code blocks are not part of
one big program. They are examples that workshop participants should
run interactively.

So, for instance, where the slideshow and handouts would have a code
block identified like so:

Listing 3: Compare geometric vs. band-limited waves, aurally.

... a student should be able to open up the corresponding code file and find:

// Listing 3: Compare geometric vs. band-limited waves, aurally.

Just wondering if anyone has done this. If not, I'm sure I can hack
something up but it would save some time if somebody has some code
lying around.

Thanks in advance --
hjh