For years, the El imprint of Cherry Red has been collecting all the strangest and most fascinating avant-garde classical pieces, electronic experiments, and oddball rarities for a fervent group of admirers.  Though their releases can be a little esoteric, El’s collections have always been able to welcome in new listeners.  And now, they offer what might be the essential introduction to twentieth-century avant-garde and classical (at least for listeners tuned to popular music).  It’s called I’d Love To Turn You On: Classical and Avant-Garde Music That Inspired The Counter-Culture, and it’s in…