"Locomotive Breath," Jethro Tull
It starts out as a classical-inspired piano piece before shifting into a jazz-rock improvisation, which then explodes into a tight-fisted heavy metal arrangement before Jethro Tull's leader Ian Anderson comes in vocally to deliver a parable on overpopulation.
Its long instrumental intro notwithstanding, "Locomotive Breath" is one of the nastiest and angriest songs Jethro Tull ever committed to disc. The song uses a passenger train as a metaphor for the population boom threatening life and earth with those in power having the powerless by the . . . you-know-what. Anderson later explained that he used the railroad metaphor based on his own experiences with transportation - he doesn't drive, he uses trains and buses to get around - and he saw it as an effective way to convey his concerns about overpopulation, which derived form an increasing reliance on cars that produced so much overdevelopment that would lead to a thinning of the planet's finite resources.
"Locomotive Breath" was included on Jethro Tull's fourth album, Aqualung, which came out 55 years ago this weekend, hence my Music Video Of the Week is Jethro Tull performing the song in Germany in July 1982. (Another Aqualung song dealing with transportation, "Cheap Day Return," deals with Anderson returning home on the London Underground after having visited his ill father; a cheap day return, in London Underground parlance, is a discounted return-fare subway ticket.) Enjoy the video.