The earliest written instrumental music uses contemporary vocal notation: the dances in Pa 844 (thirteenth century), Lo 28550 (the Robertsbridge codex, fourteenth century), Lo 29987 and Faenza 117 (both fifteenth century). The Robertsbridge codex contains a hybrid notation in which the upper voice or voices appear in conventional vocal notation and the lower voice is represented by the letter names of the notes. This system becomes the ancestor of German keyboard tablatures of the fifteenth century, which similarly use conventional and literal notation for the upper and lower voices, respectively. These developments signal independent and idiosyncratic approaches to notation that become specific for each instrument or group of instruments, which we today collect under the generic term tablature.