Gesolreut (sometimes split into the parts G sol re ut) is a music term dating to the medieval period.
It is the word used for the pitches g and g♯ within the hexachord system devised by Guido of Arezzo.
[1] It is the seventh compound name utilized in the Guidonian hand mnemonic device for sight-singing.
[2] In this method, the pitch g/g# is sung using either sol, re, or ut, depending on what hexachord is being used.
[3]