"Feelin' Alright" was written in 1968 by Dave Mason of Traffic for the band's first album, also named Traffic. Released that year as a single, "Feelin' Alright" did not chart, although it was a popular cut on album rock stations. It became better known in 1969 when Joe Cocker released it and included it on his debut album A Little Help from My Friends. Cocker re-titled the song "Feeling Alright," which was pretty odd, given his famously poor enunciation. It has since been covered many times.
Audio only:
The only full version of John Belushi I could find:
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The only live version I could find: