My "Hymn" for Mezzo Soprano with piano accompaniment was performed at the University of Texas at Arlington and Texas Wesleyan University in November. I wanted this piece to be unhindered by extra-musical lyrics, with only the vaguest idea of a extra-musical meaning indicated by the title. For that purpose, I decided to borrow a technique of one of my favorite composers- to simply make a up a fake "language" to be sung, leaving meaning up to the listeners' imaginations, and allowing them to focus more on the musical content rather than the lyrics.
Like the best laid plans of mice and composers, my idea backfired completely: rather than simply giving up when unable to understand the lyrics and listening to the music, the lyrcs became the most-discussed aspect of my piece. Various listeners have described it as a mixture of Latin, French, and Italian, some seemed to be (excessively) baffled their inability to precisely identify the language, going out of their way to ask about it weeks later, other seems to exude an aura of condecending bemusement.
It was an interesting experiment that yielded unexpected results. I think I'll try it again someday.