I'm currently in medias res preparing for next week's concerts of Pergolesi's "Stabat Mater" and Paul Crabtree's "Sedebat Mater" (with two arias by Vivaldi and Bach thrown in for good measure). I've been asked by a number of y'all how I prepare for these premieres of commissioned works, so I thought I'd sortof give a glimpse of my (very quirky) process.
The big (and probably obvious) difference between learning a work that is in the standard repertory and learning a work that was written for you is that, for the latter, there is no received wisdom in performing the piece -- no colleagues who have performed it before, no recordings with which to agree or disagree, no list of errata in the score and parts....nada. You're on your own here...
Fortunately, when working with Paul Crabtree (a great friend and the genius composer of "Sedebat Mater"), the last of the four (errors in parts/score) tend to be nonexistent, as he is a meticulous editor of his own work. This still leaves the fact that there is no roadmap of what to expect once you open the package of scores and parts from the composer.
In the case of "Sedebat Mater," I received the full score and parts about two months ago. Initially, when I receive a new score, I try (as much as possible) to spend a considerable time reading through the score and hearing the music in my head. I prefer not to, initially, play through the music at the piano or listen to a MIDI-generated recording of the work. I find that this helps me get an overall concept of what the arc of the piece will eventually resemble.
After a few weeks of silent study and singing through all the parts without the aid of a piano, I begin to start to learn the work at the keyboard, figuring out the important harmonic landmarks in the piece. With new works, this can be challenging, as rhythms and counterpoint are often purposely at odds with traditional Western musical theory, so much of my time is spent trying to anticipate what will be difficult when actual live musicians are rehearsing/performing the piece.
Once I have a reasonably good handle on the harmonic structure, I take out my colored pencils (it's like kindegarden!) and mark the hell out of the score. Everyone has a different shorthand when it comes to marking their scores -- mine is mostly to overcome my astigmatism so that I don't have to wear my glasses in rehearsal or performance. :) Big red, blue and green marks thoughout my score remind me of what I've been studying for the past few months so that I can just glance down and know what's coming next.
Finally, once my preparation is mostly done, I'll call up the composer (in this case Paul -- EXPECT A CALL SOON!) and ask him or her what THEY really feel are the most imporant musical ideas to get across. I don't really like to have this conversation until I've developed opinions of my own, based on the notes on the page.
So, yeah... A bit of insight on how a World Premiere goes from score to first rehearsal with Seraphic Fire.