The song "If You Want to Sing Out, Sing Out" was composed by Cat Stevens especially for the movie Harold and Maude in 1971.
The song also was used in 2009 by T-Mobile and Google for a cell phone commercial.
In 2007, a rendition of "If You Want to Sing Out, Sing Out" appeared in the film, Charlie Bartlett, a teen tragic comedy film for which Stevens' lyrics and music appear to be a comfortable fit.
Well if you want to sing out, sing out
And if you want to be free, be free
'Cause there's a million things to be
You know that there are