<P> "Bookends", also known as "Bookends Theme", is a song by American music duo Simon & Garfunkel from their fourth studio album, Bookends (1968). It appears twice on the track listing, as the first and last song on side one of the original vinyl LP . </P> <P> The "Bookends Theme" that opens and closes side one is played on the acoustic guitar, with no additional instruments . The song is a brief acoustic piece (once compared to English rock band the Moody Blues) that evokes "a time of innocence ." </P> <P> The reprise is preceded by "Old Friends", which segues into the song with a single high, sustained note on the strings . The reprise contains vocal accompaniment from the duo . "The text refers to the passage of time, and to memories of a loved one, and thus fittingly concludes the series of intervening songs, which address interpersonal relationships at times of life that progress from song to song," wrote James Bennighof, author of The Words and Music of Paul Simon . The piece closes the entire suite with the "resigned admonition" to "Preserve your memories / They're all that's left you ." </P> <P> The song was used in the 2009 film (500) Days of Summer . </P>

What a time it was a time of innocence