Here’s how and why Led Zep accrued all those superlatives and myths. The heaviness (“Immigrant Song” and a 26-minute “Dazed And Confused”) is one thing; quite another is the sheer grace, patrician arrogance and panache with which it’s delivered. Compare “Black Dog” and “Rock And Roll” to the proletarian flailings of Sabbath or Heep. Even compared to the relatively cultivated Deep Purple, this music is precociously adult. It turns the most taciturn critic into a groupie; you know you shouldn’t, but you want it really. It also serves to remind how ’70s metal out-wanked prog in terms of cock-rocking prolixity. Just check Bonham’s “Moby Dick” and the 23-minute “Whole Lotta Love”. But how promiscuously gifted were Bonham and Page. Of the latter’s generation, only Howe, Hendrix and Akkerman had comparable melodic imagination. OK, so he produced this. Why not a showcase? Jaw-dropping.