Throughout the 20th Century, the guitar has proven itself to be an instrument of many possibilities due to the increased interest shown by avant-garde composers. Several of these composers and/or compositions are either rarely performed, or performed with considerable difficulty due to problems of various nature. The key objective of this project is the documentation and reconstruction of the historical performance practice of such pieces. This result will be achieved through gathering information from historical performers and their collaboration with specifically relevant composers. Case studies to support the research will include music by Berio, Kagel, Lachenmann and Radulescu.