Back when people actually took the time to sit down and listen to records from front to back, nothing delivered a more rewarding experience than concept albums. Mostly based around a structured narrative, though sometimes a loose theme would tie all the songs together, concept albums were the equivalent of rock 'n' roll theater on an artsy scale. From tales of intergalactic rock stars to stories of isolated youth, our list of Rock's Best Concept Albums is filled with some of popular music's most ambitious projects of the rock era.

Frank Sinatra is widely considered to be the inventor of the concept album, thanks to his early records for Capitol -- such as In the Wee Small Hours, Songs for Swingin' Lovers and Come Fly With Me -- where he chose songs that all revolved a specific theme. But it wasn't until a reissue campaign in the '90s that marketed them as concept albums that he was given that designation.

Instead, it was the mid-'60s, when the combination of artistic ambition, increases in recording technology and psychedelics prompted rock musicians to experiment with song cycles, as Sinatra had done. Within a few years, others began writing full-length narratives, complete with characters and recurring musical themes, pushing rock into new directions.

Perhaps not surprisingly, more than half of our entires belong to two groups, Pink Floyd and the Who. Those bands built upon the earliest experiments and went on to create epic works. But we also have classic LPs by the BeatlesDavid Bowie, the Kinks and the Beach Boys. Check them out below.