Who was the lyricist who wrote over 51% of the music for the Musical "Once"  that won the 2013 Grammy Award for Best Musical Theater Album?
Once (musical):  Like the film, music and lyrics were by Glen Hansard and Markéta Irglová, including the Academy Award-winning "Falling Slowly". Grammy Award for Best Musical Theater Album:  The award was given only to the album producer, and to the composer and lyricist who wrote at least 51% of the music which had not been recorded previously.
Glen Hansard and Markéta Irglová