A quick google seems to have many good things to say about 7 string, and the answer to “whether someone should buy a 7 string” is majority “yes”, without stating possible issues. And objectively it make sense: 7 string is just 6 string with addition of low B, so on songs that don’t use that string, just don’t pick/strum it. Yet, to my knowledge, artist that use majority of 7 string are few. Aside from a few metal bands, the only other new groups I can think of that utilize 7 string is Babymetal; much less so in Blues or Rock or Pop. Even Steve Vai seems to play less on 7-string nowadays. So why isn’t 7-string guitar used more in practice? Specifically, are there some issues on 7 string (especially those on 25.5 inch scale) that a 6 string is more benefical?
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There’s a ton of harmonic possibilities with an extra low string: new voicings, inversions and more opportunities for less position changes.
The downsides? The neck is wider and usually flatter. You have to careful with how you EQ- that low B can get muddy REAL quick and gets into bass frequency range which can double the mud.
They’ve evolved to be staples in DJent and metalcore because those bands value heaviness and chunkiness in their riffs and the bass is usually much more “trebly” than in pop/rock/etc. Add in the fact that 99% of all music ever made was made on a 6 string, unless you’re doing original “heavy” type music it’s just not needed. If you JUST want the low register, you can always get a baritone guitar (BEADGB) and omit the top string.
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