Because the song-and-performer combinations were decided by lottery on the day of the examination, the examinees had to practice all songs in sahogaku, therefore, gakuko performed a significant role in handing down and sophistication of gagaku.
試験当日になってくじ引きで曲目と演奏者の組み合わせが決定されるため、左方楽の全曲目について修練を積まねばならず、したがって楽講は雅楽の伝承と洗練に大きな役割を果たしてきた。