We use classical music schema (where there are works, performances, composers, and performers) to define music entities for this site. It fits beautifully because in Vietnamese music most of the time song writers and singers are not the same; a song (work) is usually sung by many singers.
For many cases, a song is written by more than one artist: music is written by one and lyric is written by another. For many other cases, musicians take poems (of different poets) and turn them into songs. Artists sometimes also translate foreign songs into Vietnamese.

Songs and Performances

Songs (or works) are products of composers. Songs are not associated with media files; instead, it's associated with melody, with lyric. When a song is performed by a specific performer(s) and recorded by a producer, it creates a performance. Performances are associated with media files, with performers (or singers), with albums and producers. A song usually contains many performances.

Albums

Albums are collections of performances (or tracks), not songs (this is where the confusion arrives). That is why an album contains a list of media files. Albums are usually associated with feature artists (composers or performers).

Composers, Performers, and Artists

Composers are those who contribute into the creation of songs. Composers are used in this site for all song credits: melody writers, lyric writers, poets, and translators. The artist info page of a composer contains a list of songs (works) that he/she should be credited.

Performers are those who contribute into the creation of performances. Performers can be singers or intrumental players in case of instrumental music. The artist info page of a performer contains a list of performances (and therefore media files) that he/she performed.

Artists are used as a common term to address both composers and performers.