Make melodies
Like basslines, melodies are patterns of single notes. While basslines are low-pitched, melodies are generally high-pitched, and define the "identity" of the song in many styles of music; if you ask someone to sing a particular song, they'll usually sing the melody.
Melodies are often sung, but may also be played by almost any instrument.
Melodies are often much more rhythmically active than basslines, and may cover a wide range of notes.