Melody
By definition, a string of notes in a short stanza, similar to a verbal sentence. This gives rise to the Melody Line, which, for example, can be extrapolated apon.
This can be utilised by any instument/s, as solo, or harmony.
Examples:
In Jazz, a melody line is used as a concept, and experimentalised through improvisiation.
In Classical, a melody is introduced, where apon the composer creates variations thereof, and around the melody.
In Rock, Metal, Pop & Rap, it is relies hevily on melody as the basis of the song, mainly in a repeptitive manner.