When the original shamisen (a three-stringed Japanese banjo) came down to Japan, it was players of the Heike biwa who first handled it and improved it to make it similar to the present instrument.
三味線の祖型が日本に伝来したとき、これを初めて扱い現在に近い楽器に改良したのが平家琵琶の演奏家たちであった。