George Clinton reportedly told Eddie Hazel to play as if he had just learned his mother was dead — and the resulting ten-minute guitar solo on Maggot Brain is one of the most emotionally raw performances ever recorded. Hazel's wah-drenched, deeply melodic improvisation unfolds like a sustained cry of grief, with virtually no rhythm section beneath it. Carlos Santana called it the greatest guitar solo he had ever heard.

Reference:

Wikipedia: Maggot Brain

https://en.wikipedia.org/wiki/Maggot_Brain_(song)