[XeTeX] Setting greek letters in cmtt with XeTeX on OS X

[Rodney Polkinghorne]

Dear list

Has anyone used lcm with XeTeX?  If so, how do you map greek letters
in the XeTeX source to the encodings used in the lcm font files?

I'm writing a program to simulate clouds of trapped atoms.  It
involves some complicated equations, and I'm using noweb to combine
the mathematical derivations with the fortran code to solve them.  The
code uses greek letters as variables, to be consistent with the
mathematics.

I'm currently setting the text and equations in Computer Modern, and
the code in Courier New.  That works, but it's ugly.  I'd like to set
the code in Computer Modern Typewriter, but the sticking point is
those greek letters.

I downloaded the Open Type lcm files, and installed them on my OS X
box using the Font Book program.  That was easy.  Then I realised that
lcm lacks greek letters.  I downloaded the cm-lgc fonts, which are
supposed to include a greek version of cmtt.  However, these only come
as Type 1 files, which Font Book refuses to touch.  I haven't figured
out how to use them with XeTeX, either.

Am I making this harder than it needs to be?  I'm not that attached to
Computer Modern, and maybe there are other fonts where this would
simply work.

Thanks for any help you can offer.

Rodney Polkinghorne