I'm not a font person so I have no idea what a Last Resort Font, intelligent font file, Character Map, imgageable, or line layout support is and more importantly how they relate to my questions. It sounds like you're telling me how to design a font. That's beyond my scope ... Or dare I say, why do they look so great in their intended program, but not in Pages?
Not quite. You are being told how music is supported in the universal character set, and how the universal character set is supported in the system level service for mapping font-independent character codes to font-dependent glyph codes that draw glyphs on digital graphic devices.
Traditionally, music and mathematics were not multiplied using the composite letterpress printing surface, but using the engraved copper plate printing surface and increasingly through the nineteenth and twentieth century using the lithographic printing surface.
After the introduction of digital imaging devices in the nineteen-eighties, music and mathetics, like oriental writing systems including Arabic and Indic, still did not fall in the scope of the applications for composing periodicals and books in the writing systems of the Latin script.
This has produced a problem. First and foremost, the thing to avoid is to do as Dr John Warnock and CEO Steven Jobs did in order to support mathematics (including monotonic Greek) in Adobe PostScript version 23 for the Apple LaserWriter.
What they did was to draw mathematics by directly depicting the mathematical glyphs onto character codes in Apple Standard Roman. This completely chaotifies the underlying textual content, even if the typographic composition as such can be correct.
For instance, here in København we have Det Kongelige Konservatorium where a lecturer sells TrueType and PostScript Type 1 fonts at DKK 200 or thereabouts to draw music the way mathematics was drawn in the Apple LaserWriter.
This is one part of what the Library of the University of Virginia is hoping to help people not do, because a digital document that starts its life cycle with chaotified textual content does not support computerised full phrase cataloguing.
The other part of what the Library of the University of Virginia wants to help people do is work with a layout logic for music that is independent of the life cycle of particular commercial products. This is along the same lines as other projects that propose a shift from application-dependent methods and models to application-independent methods and models. This raises the problem of application support which is part of the problem you report.
IMHO you should be able to find a non-alphabetic music font somewhere that supports music in ISO-IEC 10646 and that is workable when mixed with alphabetic fonts in the line, but to lay out sheet music you would want as well a font for a music layout format as a software shaper for that music layout format. You would also want an application-independent file format that preserves searching for the music and for the lyrics. PDF is dicey on support for search.
/hh