Originally Posted by Delirium-Zero

On one side of the spectrum is the "raw" sound, which basically means almost untouched by studio engineering. It's the product of writing what you feel, playing it as you feel it, and letting the studio like, leave it as-is. There might be synthesizers involved but there's little if any post-production in the studio to make it sound more "finished". This style is taken more seriously by rock music fans, and fans of more emotional, serious, dark music. Fans of that type of music don't like the "overproduced" sound which is typically stripped of emotion through overengineering.

On the other side of the spectrum is "overproduced", where the song has been diluted by studio work into a song intended for selling to the public as opposed to a piece of "art" intended for the artist to let their feelings out. This is the slick production most pop music has. The idea is to make it as appealing to most people's ears (especially young people's) as possible, often without regard to the artist's original intent. This style is the more enjoyable one to most pop-music lovers - to them, the "raw" style sounds simply unfinished and lazy.

The instruments used don't necessarily classify it as one or the other. Where typically "raw" music is guitar- and drum-based, and typically "overproduced" music is made entirely on keyboards & synthesizers, it doesn't mean a mostly synth song can't be raw ("And Then", for example), or a mostly guitar song can't be overproduced ("Humming 7/4", for example).

I'd classify most of ayu's music in a "happy medium" part of the spectrum. Alot of it is very slickly produced, but not overproduced most of the time. It's not usually engineered at the cost of the emotional feelings that went into the song to begin with. I do, however, think that "still alone" stuffered from a bad transition from its original "raw" feeling (heard in the takanoyuri CM) into being very overproduced (resulting in the shiny, squeaky-sounding album version).