The fulfillment of this contract commenced with the release of "A Merry Little Christmas", her first holiday collection, which includes rare choral works, the somber Joni Mitchell song "River", and a rare recorded duet with the late Rosemary Clooney on Clooney's signature song, "White Christmas". Since leaving Warner Music, Ronstadt has gone on to release one album each under Verve and Vanguard Records. In 2006, recording as the ZoZo Sisters, Ronstadt teamed with her new friend, musician and musical scholar Ann Savoy, to record "Adieu False Heart". It was an album of roots music incorporating pop, Cajun, and early-20th-century music and released on the Vanguard Records label. But "Adieu False Heart" was a commercial failure, peaking at number 146 in the U.S. despite her touring for the final time that year. It was the last time Linda Ronstadt would record an album, having begun to lose her singing ability as the result of Parkinson's disease, diagnosed in December 2012. "Adieu False Heart", recorded in Louisiana, features a cast of local musicians, including Chas Justus, Eric Frey and Kevin Wimmer of the Red Stick Ramblers, Sam Broussard of the Mamou Playboys, Dirk Powell, and Joel Savoy, as well as an array of Nashville musicians: fiddler Stuart Duncan, mandolinist Sam Bush, and guitarist Bryan Sutton. The recording earned two Grammy Award nominations: Best Traditional Folk Album and Best Engineered Album, Non-Classical. In 2007, Ronstadt contributed to the compilation album ""a tribute album to jazz music's all-time most heralded artiston the track "Miss Otis Regrets". In August 2007, Ronstadt headlined the Newport Folk Festival, making her debut at this event, where she incorporated jazz, rock, and folk music into her repertoire. It was one of her final concerts. In 2010, Ronstadt contributed the arrangement and lead vocal to "A La Orilla de un Palmar" on the Chieftains' studio album "San Patricio" (with Ry Cooder). This remains her most recent commercially available recording as lead vocalist. In 2011, Ronstadt was interviewed by the "Arizona Daily Star" and announced her retirement. In August 2013, she revealed to Alanna Nash, writing for AARP, that she has Parkinson's disease and "can no longer sing a note." Her diagnosis was subsequently re-evaluated as progressive supranuclear palsy.