I remember working on the Nielsen 5 years ago, my junior year in undergrad. I remember struggling with it, as I'm sure everyone has, but never really appreciated the quality of writing and complexity with which Nielsen diligently constructed this marvelous work.
It's the 20th century counterpart to Mozart's Concerto.
You can play it until you're blue in the face - but until you study it, phrase by phrase - you never see the complexity of Nielsen's counterpoint. Or even his jovial treatment of certain phrases to the development of motives throughout the work. Nielsen definitely has a large palette of colors to choose from, particularly in his treatment and permutation of the the main motive throughout the work - ranging from intense, psychotic treatment, to weaving it through a melancholy and lyrical maze of sweetness. Even to a pseudo fugue treatment at the beginning only to move to this GIGANTIC variation on one motive.
Looking at the score, you see these amazing little interludes between the soloist and the orchestra. A beautifully choreographed ballet between two insane lovers.
A paranoid schizophrenic's love affair.
I suggest the following recordings:
Jon Manasse - although the orchestra doesn't quite do the work justice with sloppy passages, and the soloists liberties, more often then not, make very little connection between the tutti passages. However, what makes this a rather wonderful recording is Manasse's fluid and rich timbre, which makes for one fine opening and a sublime execution of the adagio sections.
Robert Frost - Always a favorite. But, as Frost is known to do, takes the technical bounds of this work to new heights. For me, I find only a few musical interpretations rather odd, but evidently well thought out - seeing that Frost is an avante-gaurde contemporary musician, his study no doubt aided in his musical decisions. A plus. His fluidity and grace are sweet contrasts to the more dark and psychotic nature of the piece. I must give him an A for this performance, capturing both the characteristic of mental insecurities of the piece to the technical demands.
Sabine Meyer - This is the one recording I find myself disappointed every time it comes across my iPod. However, it is the most solid performance of the many I have - but very straight forward. Meyer's technique, flawless - but this doesn't make up for the lack of musicality.