Question:  Andy Williams signature song was originally performed by who?
Context: The Wonderful World of Andy Williams is an album by American pop singer Andy Williams that was released by Columbia Records to coincide with the December 31, 1963, broadcast of "The Andy Williams Show".  Various tracks were recorded with members of his family, including The Williams Brothers, who joined him for a remake of his first top 10 hit, "Canadian Sunset", from 1956. The Andy Williams Show is an album by American pop singer Andy Williams that was released in the fall of 1970 by Columbia Records.  In his review on AllMusic.com, William Ruhlmann writes that "The Andy Williams Show LP was not a soundtrack recording from the TV series, and it was not really a live album, although it gets categorized as such.  What appears to be the case is that Columbia Records took a group of Williams' studio recordings, most of them made during the summer of 1970 and consisting of his versions of recent soft rock hits, and added a lot of canned applause along with some of the kind of musical interludes used to usher numbers on and off on the show, including bits of its "Moon River" theme music at the start and the finish." Andy Williams' Greatest Hits is a compilation album by American pop singer Andy Williams that was released in early 1970 by Columbia Records.  It was not, however, as its title might suggest, strictly a hit singles compilation, although some of his biggest songs since joining Columbia (such as the easy listening number ones "Can't Get Used to Losing You" and "Happy Heart") were included.  A couple of selections ("Born Free" and "More") were never released as singles by Williams, and his signature song, "Moon River", was released in the 7-inch single format but only for jukeboxes.  His six Cadence singles that made the Top 10 on "Billboard" magazine's Hot 100 are passed over for the inclusion of his number 11 hit from that label, "The Hawaiian Wedding Song", and 17 of his Columbia recordings that made the Hot 100 up until 1970 are left out here in favor of "Charade", which spent its one week on the chart at number 100. The Andy Williams Show was an American television variety show that ran from 1962 to 1971 (alternating during the summer of 1970 with "Andy Williams Presents Ray Stevens"), and a short-lived run in syndication, beginning in the fall of 1976.  It was hosted by crooner Andy Williams. "Moon River" is a song composed by Henry Mancini with lyrics by Johnny Mercer.  It was originally performed by Audrey Hepburn in the 1961 movie "Breakfast at Tiffany's", winning an Academy Award for Best Original Song.  The song also won the 1962 Grammy Awards for Record of the Year and Song of the Year. "Dear Heart" is a song written by Henry Mancini, Ray Evans, and Jay Livingston and performed by Andy Williams.  The song reached #2 on the U.S. adult contemporary chart and #24 on the "Billboard" chart in 1964.  It appears on the 1965 Andy Williams album, "Andy Williams' Dear Heart". Andy Williams recorded 43 studio albums, 17 of which (along with the 1970 compilation "Andy Williams' Greatest Hits") received Gold certification from the Recording Industry Association of America for selling 500,000 units.  Three of those recipients went on to reach one million in sales, for which they were awarded Platinum certification.  Between studio, Christmas, and compilation albums he had 37 entries on the pop albums chart in "Billboard" magazine with 12 of those making the top 10.  One of those 12, his 1963 album "Days of Wine and Roses and Other TV Requests", spent 16 weeks at number one and comes in at number five on the list of the top albums released in the 1960s in terms of "Billboard" chart performance.  During the 1960s and early 1970s two of his Platinum LPs, "The Andy Williams Christmas Album" and "Merry Christmas", made annual appearances on the magazine's Christmas Albums chart, where they each reached the number one position in multiple holiday seasons.  In a ranking of the top album artists of the 1960s in terms of "Billboard" chart performance, he comes in at number eight. "Lonely Street" is a 1958 song written by Carl Belew, Kenny Sowder, and W.S. Stevenson, originally performed by Belew.  Its most successful rendition was by Andy Williams, whose version reached #5 on the "Billboard" chart and #20 on the R&B chart in 1959.  The song appeared on his 1959 album, "Lonely Street".  Archie Bleyer's Orchestra played on the song. Andy Williams' Greatest Hits Vol.  2 is a compilation album by American pop singer Andy Williams that was released in June 1973 by Columbia Records.  This collection follows in the footsteps of its predecessor, "Andy Williams' Greatest Hits", in that it is not limited to his biggest and most recent hit singles, although his final two US Top 40 entries ("(Where Do I Begin) Love Story" and "Speak Softly Love (Love Theme from 'The Godfather')") were included.  It also has an album track not released as a single ("The Impossible Dream (The Quest)"), a couple of hits from his time with Cadence Records ("Lonely Street" and "The Village of St. Bernadette"), two other singles that could have been included on the first volume ("In the Arms of Love" and "Music to Watch Girls By"), and two Easy Listening chart entries that never made the "Billboard" Hot 100 ("Home Lovin' Man" and "Music from Across the Way"). The New Andy Williams Christmas Album is a live Christmas album by American pop singer Andy Williams that was digitally recorded live in concert at the Andy Williams Moon River Theatre in Branson, Missouri in 1993 and released by the LaserLight division of Delta Music Inc. in 1994.  It includes performances of songs that he had previously recorded for his four solo holiday releases as well as a new spoken word track ("Jimmy Bishop Christmas Column") that briefly summarizes the life of Jesus Christ.
Answer: Audrey Hepburn