Guitarists often use altered tunings in order to achieve different sounds and sonorities. Most tunings involve lowering the pitch of a particular string. For example, countless classical guitar pieces require the 6th string to be lowered to D. Guitarists playing lute repertoire often lower the G string to F#. Then there are tunings used by folk guitarists, such as the popular DADGAD tunings. Some electric guitarists lower the pitch of every string by a half step.
Much less common is to raise the pitch of a string.
In this inventive study (Fernando Sor's Op. 35, No. 12), the 6th string is raised half a step to F. This allows for some chords and fingerings that wouldn't be possible with a regular tuning.
Explore the various possibilities afforded by this unusual tuning and try out different fingerings with your teacher. To this end, fingerings have been omitted from the following PDF: