I don't know if Mark Clark is on the abcusers list so:

Hello,

I'd like to announce the initial release of freeware Win32 software
that translates ABC to MusicXML and back again. MusicXML is an
emerging standard for music notation that allows interoperability with
different notation packages, such as Finale, SharpEye, Tabazar and
others. See www.musicxml.org for more info.

The software is available from
http://home.austin.rr.com/johner/abc2xml

A brief overview of why you might find this software useful follows.

Thanks,
John Lynch

Reasons you might want to translate ABC into MusicXML include the
following:

interoperability
    import tunes into any program that can read MusicXML,
    including Finale, TaBazar, and (soon) Igor Engraver.

analysis
    once a tune or tuneset is in MusicXML format, reports
    can be generated using any tool that can read XML, such as XSL

transformation or generation
    tools like XSL can also be used to transform the music in
    various ways, then, if desired, xml2abc can be used to turn
    the XML back into ABC. This allows a wide variety of musical
    modifications to be encoded using any tools that manipulate XML

The main reasons you might want to convert MusicXML to ABC are:

file creation
    any tool that can output MusicXML can be used to create ABC files.
    For example, Finale can be used for MIDI or notation-based input;
    SharpEye can be used for OCR input.

typesetting
    basic typesetting of MusicXML files can done with programs like
    abc2ps

transformation
    in conjunction with abc2xml , ABC files can be converted to
    MusicXML, transformed with an XML tool like XSL, then converted
    back to ABC. This allows a wide range of operations to be
    performed on ABC files without ever parsing ABC.

Jon