Gagaku and Heikyoku are music with absolute pitch so the Gakubiwa and the Heike biwa are instruments with perfect pitch, and they are different from the Biwagaku, music with relative pitch, after the early-modern times.
雅楽と平曲は絶対音高の音楽であるため、楽琵琶と平家琵琶は絶対音の楽器であり、相対音高の音楽である近世以降の琵琶楽と異なる。