In spring 1969, after three acoustic Tyrannosaurus Rex albums and an equal number of singles released to limited appeal, Bolan began to make the transition from basing his band's sound around an acoustic guitar to basing it around an electric one. The new electric sound was premiered on single "King of the Rumbling Spires" and tracks were recorded for a planned fourth album, before Bolan replaced percussionist Steve Peregrin Took with Mickey Finn following a US tour. Shortly thereafter, the new duo completed the fourth album "A Beard of Stars" (including some material salvaged from the final Took sessions). This was released in early 1970. Later that year a fifth album, "T. Rex", was recorded under the band's new shortened name of T. Rex.