Soprano Tony Arnold has written an informative blog post on the challenges inherent in singing the vocal music of Elliott Carter. Brief as it is, it has implications beyond the ostensible topic and says a lot about Carter's aesthetic in general.
On a side note, I have difficulty reading musicological articles. They can be so technical as to be either confusing or soporific, and frequently they are more about other musicology than about the music itself. Tony's post, written from the standpoint of a teacher and working musician, avoids both pitfalls.