Number/Demonstrative + 首 + 歌/诗
The classifier 首 (shǒu) is the measure word used to count songs and poems. When referring to a specific song, use a number or demonstrative followed by 首, such as 这首歌 (this song) or 一首歌 (one song). It is the standard classifier for musical compositions and poetry.
这首歌是我最喜欢的,百听不厌。
zhè shǒu gē shì wǒ zuì xǐhuān de, bǎi tīng bú yàn.
This song is my favorite; I never get tired of listening to it.
他为电影写了三首歌。
tā wèi diànyǐng xiě le sān shǒu gē.
He wrote three songs for the movie.
你听过这首新歌吗?特别好听。
nǐ tīngguò zhè shǒu xīn gē ma? tèbié hǎotīng.
Have you heard this new song? It sounds really good.