One of the major issues arising from that interrogation concerned the dichotomy evident in the musical syntax of Black Sabbath and Led Zeppelin. The dichotomy that emerged reflects the very different extent to which each transgressed the blues context of their starting point. Interrogating the details of those transgressions and highlighting not only the ensuing dichotomy but also the way in which each band significantly influenced the generic evolution of heavy metal and hard rock. The compositions of Black Sabbath therefore clearly privilege instrumental textures and this concept first emerges in the experimental blues of the Yardbirds and Cream. Whilst Led Zeppelin also built on the achievements of the Yardbirds, theirs was a truer reflection of original context. For example, as mentioned earlier, Led Zeppelin emerged from the New Yardbirds. The experimental blues concepts of the Yardbirds and then the New Yardbirds naturally culminated in the work of Led Zeppelin.