This was written by Graham Gouldman, who later formed the band 10cc.

Gouldman was a prolific songwriter who also came up with songs for The Hollies, Cher, The Shadows, and Herman's Hermits.

For The Yardbirds, he provided three of their hits, also composing "Evil Hearted You" and "For Your Love." Yardbirds drummer Jim McCarty said in our 2010 interview: "'Heart Full of Soul,' which was very moody, gave us the ability to play the riff in sort of an Eastern way, give it an Oriental touch. Another very good song."

Lead guitarist Jeff Beck employed an early use of a fuzz box on his lead part. The original arrangement called for a sitar playing the lead guitar part, but they instead opted for Beck's sitar-sounding guitar.

Drummer Jim McCarty (August 2011): "[After 'For Your Love'] We were actually quite pleased that we finally had a big hit. We felt that now we could carry on and move onto the next level as a band. Definitely having a big hit opened us up to bigger venues and nationwide tours.

Then Graham came to us with 'Heart Full Of Soul' and we felt that was the perfect follow up. It became a hit as well and we were on our way. We knew we were now in a position where we had to come up with hit singles on a regular basis. But we were all for it and were happy to carry on and start experimenting."