A.Berg: Canons & vocal Fugues a 3
Those Fugues for two voices are found in the Musicdepartment of the Austrian National Library with the Signatur F21.Berg.33i Mus and F21.Berg.34 Mus (which is currently not online available). While there are no explicit advice for the performance the notation in old Vocalkeys and the consequent restriction to the certain Range of the Voice of a certain Vocalkey allows at least to perform this fugues with Voices. As far I know this the very first realisation of those pretty clean and ambitious made Fugues. The "Canons" are not more than first attempts to combine a certain Subject of a fugue with it self, to test his suitability.