Jethro Tull is one of the 3 greatest bands ever to exist. Ian Anderson is both a musical and lyrical genious: he writes amazing music and performs it wonderfully. Martin Barre is a graverly underrated musician... Most of their albums from the 1969-1979 period are masterpieces (Stand Up, Benefit, Aqualung, THICK AS A FUCKING BRICK, Minstrel in the Gallery, Songs from the Wood and Heavy Horses).
Last thing; Thick as a Brick is just mind-blowing. Buy it now and understand the power of flute.