Question: What actress and singer who played a starring role in "Grease" was a special guest during the Mormon Tabernacle Choir's 2015 Christmas shows? 
Sentence (from "Hallelujah! (Mormon Tabernacle Choir album)"): was recorded during the Mormon Tabernacle Choir's 2015 Christmas shows in the LDS Conference Center, with special guests Broadway star Laura Osnes, actor Martin Jarvis, and guest soloists from the Metropolitan Opera (Erin Morley, Tamara Mumford, Ben Bliss, Tyler Simpson).
Relevant evidence: Yes