Set the stage. Besides handling the obvious steps of identifying the work and its artist, the opening of the paragraph should state its topic and give some indication of the content to follow.
Take a position on the song's message and sound. Back up your view with lyrics from the song if applicable. Be aware that the use of quotations from a song must be more restrictive than the use of quotations from longer works of art, if you are to be compliant with the Fair Usage Doctrine of copyright law. Put quotation marks around the title of the song when you cite it, and italicize or underline the title of the album when it is cited. Some points of discussion can be an interpretation of the meaning of the song or an analysis of the song's relevance within its genre. What new direction or directions does the song suggest, for the artist in question? Consider comparing the musical work to other works by the artist.
Pay attention to tempo, instrumentation, lyrics, musicianship, dynamics, rhythm and other considerations. In addressing tempo, for instance, employ the vocabulary of musicians. With classical works, consider applying terms such as "largo" for slow, "andante" for a slightly upbeat tempo or "presto" for very fast. Capture the song's expressiveness in words. Extol its finer qualities. If it features a rich harmony or a moving solo, be sure to say so. Better yet, create fresh and appealing metaphors to characterize these traits.
Explain to the readers what instruments stand out in the song or what unique instruments are used to create a sound. Point out certain parts of the song where you can hear said instruments best or where they sound particularly interesting or out of place. Include a remark about the background of the piece or tune if possible. This remark could be a comment on where the piece was recorded or what the inspiration was behind the song.
End the paragraph with a thoughtful idea about the music or a recommendation on where the reader can find more information on the work or its performer or creator.