“Question”, The Moody Blues, 1970.
While the peak year for the Moody Blues would be 1972, they had actually become a fairly popular band in 1970. The album that they released that year, A Question of Balance peaked at #1 in the UK and #3 in the US. The only single from that album, “Question” would peak at #2 in the UK but only reach #21 in the US.
Still this album is a sign of things to come. Progressive Rock may not have been a big thing in 1970, but it would be one of the dominant sounds of 70’s Rock.