6. Songs in the Key of Life (1976), Stevie Wonder

In 1974, Stevie Wonder was the most critically revered pop star in the world; he was also considering leaving the music industry altogether. So when 'Songs in the Key of Life' was released two years later, demand was so high that it became, at the time, the fastest-selling album in history.

The album, which runs nearly 90 minutes, is effortlessly melodic, broad in scope, and deeply personal. Sonically, culturally, and emotionally, 'Songs in the Key of Life' is much more than a gigantic collection of songs - it forms an entire worldview.