That's nice I guess, but my point was that there was a lot more going on in 90s music than just grunge rock (or whatever "alternative" and "indie" mean).

I don't understand how do you get from a combination of influence, quality, and diversity to sales.

The key is to find an album that embodies their decade for different reasons. Here's another example. I chose the White Album for the 60's because, even though it came out in 69, it took the blues and psychedelic pop and rock of the 60's and many other major 60's influences and made them as top notch as one could get. The 60's were all about psychedelia, blues, pop and rock. The Beatles' White Album was all about them. Sales can play a part, but I would hardly say Pink Floyd's DSOTM was the defining album of the 70's because it bare;ly brushes upon anything the 70's as a wehole was about.

The 70's was ABOUT disco, funk, pop rock, and some prog. The idea is to find an album that's more ABOUT what the decade was about than most albums. The cultural impoertance and overall quality as one, but not necessarily sales. I mean, if we're only talking sales, hpow many artists are influenced by Shania Twain or Celine Dion?

In that case, we're talking more about importance beside defining. When you mention defining, I'm more thinking of the album that made the decade what it's known for, not an album that is influenced based on the genre the decade is known for.

For example, you chose the white album, but I was thinking we were supposed to choose an album that made it easy to choose the white album in the first place.

Exactly. That's what I'm talking about. Attempting to find the "spirit of the 90's" or whatever decade in the form of an album.

Alright, well i'll see what I can come up with.

Being the "Grungeman" and the self-proclaimed purveyor of all things Grungy, I naturally assume you would think Nirvana's second album, Nevermind, which is considered by most their first album as the defining moment of the 90s. ... but what about 311 aka "The Blue Album" by 311 in '95? It went triple platinum! ... or "Third Eye Blind" in '97? The eponymous debut studio album by the band, Third Eye Blind. I am sure they define the 90s too for a lot of people.

To be honest, Nevermind doesn't even reach my top fifteen grunge albums. I think it's excessively overrated. But at the same time, I don't deny it's diversity, and how much of an influence on modern music it has had. I can't stand some of Cobain's lyrics, notably on reed and Territorial Pissings.

Two undeniable records which were the future of music for their time:

Donna Summer - "I Feel Love" (1977) 12" single - the first pop song to feature an entirely synthesized backing track. David Bowie famously said:

And a few years later in 1981 Manuel Göttsching recorded E2-E4. Released in 1984 it set the stage for the entire techno genre that followed.

I would say Portishead's Dummy for the 90s