穆护砂，玉管朝朝弄。
清歌日日新。折花当驿路，寄与陇头人。
穆护砂， refers to an ancient musical instrument called "Mo Hu Sha". It is made of polished jade and produces a delicate and melodic sound when played.
玉管朝朝弄。(玉管：a jade flute; 朝朝：every morning; 弄：play) The poet is describing the scene of the Mo Hu Sha being played every morning, producing beautiful and refreshing melodies.
清歌日日新。(清：clear; 歌：song; 日日：every day; 新：new) This line means that the song played on the Mo Hu Sha is different and refreshing every day. It highlights the creativity and ever-changing nature of the music.
折花当驿路，寄与陇头人。
折花 (pick flowers) refers to the poet picking flowers along the road. 当驿路 (along the road) implies that the poet is traveling. 寄与 (send to) 陇头人 (a person from Longtou) means that the poet is sending the picked flowers to someone from Longtou.
Overall, the poem expresses the poet's admiration for the beautiful and melodious music produced by the Mo Hu Sha. The constantly changing melodies and the act of picking flowers along the road convey a sense of freedom, creativity, and appreciation for nature. The poet then sends the flowers as a gift to someone in Longtou, adding a touch of romantic sentiment to the poem.