Shattered Norns* and Mistworld settings.
So where am I going with this as it relates to the bard?
Well... in the Shattered Norns setting, there is a city in the Norns world called Porthvælving. It has a mirror on the Shadow Plane known as Liminenerrea. In Liminenerrea, there is a high-level harpist/mage who can assist the PCs in traveling by dream (from the Shadow Plane to the Material Plane). This concept of the harpist (which is a character type Steve is currently using), has its roots in something Steve was working on in the same era as the planes book... a harpist class that he was "collaborating with Gary Gygax on as a possible replacement for Bards for use in a campaign that has a focus on using the planes of reality and on a class that actually uses music for magic."1
Envisioned by Steve, the harpist is very Orphic, but not necessarily Orphist. The harpist appears in two variants—the song seeker and the song smith (the first with a prime requisite of Charisma, and the latter with a prime requisite of Wisdom). As a harpist rises in level, he or she becomes "in harmony" with a number of muses (the 9 Greek muses, Clio, Urania, etc.), each of which has a particular domain (history, astronomy, etc.), and with a number of graces (the 3 Greek graces, Aglaea, Euphrosyne, and Thalia). Additionally, the harpist gains song levels and uses them to improve his or her skills (which come from the graces). So, yeah... it's pretty Greek. (An interesting counterpoint to the Norse/Celtic/English/French mutt that is the Doug Schwegman bard.)
As the Marsh harpist was written, it seems more like a framework than a complete class. For example, the use of songs is noted as being akin to divine intervention in Empire of the Petal Throne, but there is no "translation" beyond that into something self-contained and usable. There aren't even any examples of how the songs were to be used (other than that they are related to the domains of the muses).
I know that to stop now will be to leave you hanging, but I'll have to admit that this post is "to be continued." I'm waiting to hear back from Mr. Marsh with some additional insights, and with the hope that I'll have enough information to be able to adapt his original harpist vision into a BX/LL character class.
* On a side note, I'll be making a BIG announcement soon regarding the publication of a Shattered Norns adventure!
1 Per the Shadows Beneath NTRPG Con Scenario Part Two document.