A music accompaniment is background musical support for a melody or vocal line in a piece of music. Writing an accompaniment to music is an art form that takes a lifetime to perfect. Each piece of music is different, formed in varying styles and genres, and each vocalist brings his own facet to the piece as well. Certain aspects of writing music must always be considered when writing an accompaniment. Begin with a working knowledge of reading and writing music and create the addition to the piece you need.
Determine whether the vocalist is a male or female. The vocalist determines the range and overall sound of the music. Avoid voicing the chords too high for a female vocalist, or it will clash with the piano, guitar or other instrument.
Look at the contour of the melody line in the music to determine whether the melody moves at a slow or fast pace.
Harmonize the melody of the piece. Place chords underneath the melody in order to outline the melody throughout the piece.
Determine the rhythm of the bass line. Consider whether the bass line is a slow rhythm that supports movement in the middle voices or whether the bass line does something faster and more rhythmic.
Make the overall accompaniment represent the dynamic integrity of the melody. Create a loud accompaniment for a melody voice that gets loud, and create a soft accompaniment where the melody voice gets soft. Match the dynamics of the melody throughout the piece.