Complex sentence: Jarrett was a member of the Mormon Tabernacle Choir from 1999 to 2008 and from 2008 until May of 2011 he served as an assistant to former Mormon Tabernacle Choir president, Mac Christensen.
Split into simpler sentences: Jarrett was a member of the Mormon Tabernacle Choir from 1999 to 2008. From 2008 until May 2011, he served as an assistant to former Mormon Tabernacle Choir president, Mac Christensen.