The band became the first supergroup of progressive – that is, the band in which each member was known and popular before the merger. The fourth member of the band would have been – who do you think? – Jimmy Hendrix, and the band would have been called HELP after the first letters of the musicians’ last names. But that didn’t happen because of Hendrix’s death in 1970, and ELP began to create in threes.
Their music was imbued with a love and awe for classical and operatic music, which they combined with hard rock and emerging stadium rock music. It was from these musicians that many stadium bands (e.g., Queen) later learned. The majesty and solemnity of ELP’s compositions are remarkably matched by the drive of rock music. This is despite the fact that in many compositions they do not use guitar at all.
ELP always liked long formats and conceptual albums, so it’s better to listen to the music by albums. Tarkus and Trilogy are good to listen to.