Extended range guitar

English Wikipedia has an article on:

List of extended-range guitar players

An extended range guitar is a guitar with more than 6 strings. For microtonal instruments, e.g. the Kite guitar, this may not actually increase the range.

For acoustic guitars, Rozini and Ibanez tend to have wider fingerboards than the Eastern European ones.

General resources

Forums

• SevenString.org

Models

Sources for 7- and 8-string guitars, both acoustic and electric:

Low-end (US$200-400)

Grote (China)

7-string archtop semi-acoustic

Very favorable review that claims it's a great value for the price:

https://riverheightsmusic.com/grote-guitars-review-7-string-arch-top/

Trembita (Ukraine)

7-string steel string

https://trembita-guitars.com/index

Leo Tone (Ukraine)

7-string steel string with tight string spacing

https://www.amazon.com/Russian-Guitar-Acoustic-Classical-Cutaway/dp/B00L2K6DJY

Somewhat unfavorable review:

https://www.youtube.com/watch?v=NZd1b-yJqrs

Jackson Dinky

7-string electric

Mid-range (US$500-1200)

Agile

various 7 and 8 strings, sold in the US by Rondo

https://reverb.com/shop/rondo-music

Ibanez (Japan)

various models

https://www.ibanez.com/usa/products/search/electric_guitars/list/?cf_search_strings=7&cf_search_strings=8

discontinued 7-string classical: https://ibanez.fandom.com/wiki/G207CWC

High-end (US$1200 and up)

Ovation

Custom Elite 8-string steel string w pickup

Discontinued, sometimes available used. Retail price was $1200-1600 new. Won't fit in most cases.

Rozini (Brazil)

7 and 8 strings

https://rozinibrazil.com/en/categoria_de_produtos/guitars/

Kremona (Bulgaria)

https://www.kremonausa.com/en/performer-series/fiesta-cw-7-kremona USD$1600

Their website claims they can make any sort of custom guitar, so they might make a microtonal one?