Scheme-sandbox on MAC

[Joseph Austin]

I'm a relative newbie to Lilypond, 
using 2.16.2-1 on Mac OSX 10.6 (Snow Leopard).

I want to try some modifications, 
and am trying to work through the tutorial in: 
Manuals > Extending > Scheme Tutorial.

I haven't been able to get the scheme-sandbox to work.

I've downloaded:
> lilypond-2.16.2-1.darwin-x86.tar.bz2 Dated Jan 4, 2013, 3:47 pm       

and copied the file:
lilypond.app
to my Application folder: Macintosh HD /Applications 

I can start Lilypond from the Terminal window with:

> MacTechDaddy:~ josephaustin$ open -a lilypond.app

But when I try to start the sandbox, I get a "file not found" error:

> MacTechDaddy:~ josephaustin$ open -a lilypond.app scheme-sandbox
> The file /Users/josephaustin/scheme-sandbox does not exist.

Is there something missing from my Lilypond installation?
or do I need a different command syntax?

Otherwise, Lilypond seems to be working.  
It generates scores, and even outputs scheme per the tutorial, for example:

> {
> #(with-output-to-file "C.txt"
> (lambda () #{ \displayMusic { c'4\f } #}))
> }

(The scheme output goes to C.txt in the same directory as the source .ly file.)


Any help will be appreciated.

Joe