The guitar and the piano perform similar roles and occupy overlapping frequency ranges in jazz and popular music.
However, the piano can produce two or more simultaneous voices at the extremes of its range using standard technique. The guitar cannot produce two or more simultaneous voices at the extremes of its range using standard plucking or finger-picking techniques.
Thus the two-hand touch technique was developed partially to emulate the right and left hand of a pianist. The tuning of the guitar was altered to provide an extended low range in order to facilitate bass voices more effectively.
The result is an overall method for playing the guitar which provides the ability to effectively perform counterpoint, melody, chord and/or bass accompaniment with an extended range of the guitar that is fully utilisable.