I'm going to buy a new flute and I'm already curious to know the meaning of this phrase lol
Adding on to @Tang Ho's answer, it's from 《魔道祖师》, a light novel, written by 墨香铜臭. It was made into a TV show, known as “陈情令” thus you see "陳情" in red on the left.
Some more context on the poem, 魏婴, the main character in the novel was backlashed （反噬）as he used the power of the ghosts （修鬼道） and was framed causing him to jump off a cliff (and dies). He was then suppressed by a magical spell as a spirit/ghost for 13 years, while his friend，蓝忘机, waits by the spell for 13 years trying to bring him back. 《忘羡》is a unique song that 魏婴 used to master.
(So this is a poem about 蓝忘机's persistence in waiting for his friend)
It is a poem from a light novel
问灵十三载 - Asking the spirits for 13 years
等一不归人 - Waiting for a person who never returned (dead maybe?)
忘羡一曲远 - Wàng Xiàn's Song has faded afar
曲终人不散 - The song had ended but the persons have not departed (in spirit maybe)
Sounds like a synopsis
陳情 - Chen Qing (the author?)