“English progressive rock giants Jethro Tull are a unique phenomenon in popular music history,” (AllMusic). “Led by enigmatic frontman Ian Anderson — a singer, songwriter, guitarist, and rock’s premier flutist … their mix of heavy rock, flute-led folk melodies, blues licks, surreal, impossibly dense lyrics, and overall profundity defies easy analysis, yet in their 1970s heyday, they garnered a massive level of commercial success, notching a string of gold and platinum records and securing their place within the classic rock canon with releases like Aqualung (1971), Thick as a Brick (1972), and A Passion Play (1973). Even as critics cooled on them, Tull remained popular through later phases with their folk-rock records of the late ’70s, the electronic experimentation of the early ’80s, and eventually a Grammy Award-winning return to hard rock with 1987’s Crest of a Knave.
Benefit (1970) was the album on which the Jethro Tull sound solidified around folk music, abandoning blues entirely. Beginning with the opening number, “With You There to Help Me,” (Ian) Anderson adopts his now-familiar, slightly mournful folksinger/sage persona, with a rather sardonic outlook on life and the world…”
The mid-tempo track “Teacher” is built in A major overall, but the chorus features a D major/minor mix and then an instrumental section in B minor (first heard at 0:48 and 1:02). The pattern continues with verse 2.