Recording just a single album can be an incredibly difficult and time-consuming process (just ask Dr. Dre or Axl Rose), but these six artists took up the challenge (and succeeded) of recording two albums at once (or even more).

1. Radiohead

After the massive success of their third album OK Computer, Radiohead found it tremendously difficult to record a follow-up, as the band couldn't come to an agreement on what direction to take. Eventually, the band adopted a more abstract, experimental style and spent a staggering 18 months in the studio. From these sessions came two of Radiohead's most challenging albums: 2000's Kid A and 2001's Amnesiac.

2. Frank Zappa

Frank Zappa was a restless musician, and would frequently release multiple albums within the span of a year. Two of his most famous albums from his '70s period - 1973's Over-Nite Sensation and 1974's Apostrophe (') - were mostly recorded at the same studio sessions in spring 1973. Perhaps not coincidentally, these albums became two of Zappa's biggest commercial successes.

3. Tim Buckley

It would be impressive enough for an artist to record a single album in just one month, but avant-folk singer Tim Buckley managed to record two full-length albums in September 1969: Blue Afternoon and Lorca. Though they were recorded simultaneously, the two albums are quite different; Blue Afternoon is an ethereal folk-jazz record, while Lorca is more dark, menacing, and meandering.

4. System of a Down

It may be hard to believe now, but there was a time not too long ago when a metal band (an aggressively weird one at that) could top the Billboard charts and perform on Saturday Night Live, and System of a Down was that band. In 2004, System of a Down recorded a double album called Mezmerize/Hypnotize, but decided to release both halves separately, six months apart from one another.

5. Green Day

In 2012, Green Day embarked on a project that was somehow both simpler and more complex than their platinum-selling successes from the '00s. Instead of making another lengthy punk opera LP such as American Idiot or 21st Century Breakdown, they recorded three albums at once, which were then released separately towards the end of 2012 under the names ¡Uno!, ¡Dos!, and ¡Tre!

6. Justin Timberlake

For a pop star as big as Justin Timberlake, it's remarkable how infrequently he releases music. After his smash 2006 album FutureSex/Love Sounds, seven years went by without a new album from the former NSYNC member. In 2013, however, Timberlake made up for lost time by releasing two albums he had recorded at once: The 20/20 Experience and The 20/20 Experience - 2 of 2, released six months apart.

What other artists recorded two albums at once? Let us know down in the comments section!