Rhiannon Giddens, along with guitarist Bill Frisell and percussionist Francesco Turrisi, perform “Julie’s Aria” from Giddens’ first opera, Omar. Premiering at Spoleto, the opera is receiving productions at a number of prominent houses. Here is an audio stream via YouTube. Giddens is busy with myriad projects, but her singing is so compelling here: dare Spoleto offices hope for a cameo?