It's more for guitars, but it means turning the mids down on the EQ and boosting the EQ for bass and treble
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Quote by DisarmGoliath
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It makes the bass and treble higher than the mids. Normally the bass and treble will be equal. It is used lots by metal players.

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The advantges to using it are a more dynamic, full sounding tone, but at the same time, without mids you lose alot of "punch". As said above, it's common in metal, but not so much in other genres.
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The problem with scooping mids is that the bass guitar already occupies the bass frequencies, and the cymbals occupy the treble frequencies, so the guitar's voice is mostly in the mids. Scooping them might sound great when you play by yourself but once you add the whole band the guitar disappears, and turning up the volume doesn't help much at all, it just makes your ears hurt. Mids are good.
Not a big fan of scooped mids. My Metal Setup:

Gain:9 (cranked to ten if the riff has squeelies)
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Modulus: 1991 Q5

Marshall: MG30FDX
Acoustic: B200
The mids are just important for being heard as a bassist too. The mids are the frequencies to which the human ear has the greatest sensitivity, as they correspond with the sounds of human vocalizations. Note how if you crank the low mids, you get more "uuuu", a little bit higher more "ohhhhhh", then in the higher mids more "aaaah" and "eeee".
It's not exactly bad. The guitarist in my band does, just not to the extreme.

It creates that "air-getting-sucked-out-of-the-room" brutalness.
Quote by breakdown123
Is there such a thing as a heavy riff with out chugging on the e string?