法華經義記 1.101

1.101

「有四乾闥婆王」，此下四神是帝釋俗樂神。初言「樂乾闥婆王」者，直樂神無音聲者也。「樂音」者，有音聲者也。「美乾闥婆」者，無音聲中勝者也。「美音」者，音聲之中勝者也。

'There were four gandharva kings': the four spirits below are Śakra's mundane musicians. First, 'Music Gandharva King': pure instrumental musicians who have no vocal sound. 'Musical Sound': those who have vocal sound. 'Pleasing Gandharva': those who are superior among those without vocal sound. 'Pleasing Sound': those who are superior among those with vocal sound.