Eleven-string alto guitar
The 11-string alto guitar is a multi-string classical guitar, which generally refers to classical guitars with more than six strings. Classical guitars with extra strings can have from seven to 13 or more strings. However, an 11-string is the most useful for performing lute music, particularly Bach and Weiss. The first six strings are tuned in the same intervals as the normal classic guitar. Therefore, a musician can play with conventional fingering on those strings.
In the United States, luthier Walter Stanul makes performance instruments ranging from 11 to 13-strings called the Archguitar. The design and the body shape of this guitar is similar to the vihuela, and thus it is fundamentally different from the Bolin design.