Keyboard accompaniment is about more than finding chord shapes. The timing and spacing of the notes determine whether the same harmony becomes an atmospheric pad, a rhythmic stab or a flowing arpeggio. These ideas transfer directly to MIDI composition.
Four related chords
A useful starting cycle in C major is C–Am–F–G. Their root-position notes are C–E–G, A–C–E, F–A–C and G–B–D. These chords share a key but have different roots and characteristic relationships.
Harmonic rhythm
Harmonic rhythm describes how often the underlying chords change. Holding C major for a full four-beat bar gives one chord change per bar, even if you attack C–E–G four times. Changing to Am halfway through the bar increases the rate of harmonic change without altering tempo.
Block chords and repeated attacks
Holding a chord creates a continuous harmonic backdrop. Repeating it on quarter notes creates four attacks per bar in 4/4; playing on eighth-note subdivisions creates eight attacks. The pitches remain identical while the feel becomes more active. Dynamics, articulation and rests can change the result further.
Arpeggios and broken chords
When chord tones sound one after another, the result is a broken chord or arpeggio. For C major, C–E–G–E is a four-note sequence built entirely from triad tones. As eighth notes it becomes a different rhythmic figure without changing the chord. Such patterns are common in synthesiser parts and keyboard accompaniments.
Left-hand bass
A simple division of labour places a low chord root in the left hand and chord tones or a melody in the right. For C–Am–F–G, the roots are C–A–F–G. These bass notes make harmonic changes apparent, while the upper notes can be sustained or repeated. The bass does not always have to play the root; another chord tone at the bottom creates an inversion.
Voicing and movement
Root-position chord changes may produce large movements. Inversions rearrange chord tones across registers and can retain common notes between changes. Close voicings fit into a narrow upper range; open voicings spread tones further apart. Neither is automatically better; register, sound choice and musical context determine what works.
Overdubbing and MIDI
Producers can record a bassline and chords separately, even if they cannot play both parts in real time. MIDI retains pitch, timing, velocity and duration information, making it easy to edit articulation or vary arpeggio patterns. The fundamental musical task remains choosing how and when each harmony should sound.
Explore related articles in How Music Works — Volume 2.