Pedal
A held or repeated note, usually in the bass, while the chords above it change. Some chords will be consonant with the pedal, others dissonant: the tension arises precisely from the friction.
- Tonic pedal: C under C – F/C – G/C – C. Stability, a “home” effect, typical of intros and outros.
- Dominant pedal: G under C/G – Dm7/G – G7 – Ab/G – G7. It accumulates expectation: in sonata form it precedes the recapitulation, in EDM it precedes the drop.
- Inverted (upper) pedal: the held note is on top (a violin on E above C – Am – F – G).
- Double pedal: tonic and fifth together (drone).
Ostinato
A figure (rhythmic, melodic or harmonic) repeated while the rest changes. It can be a bass riff, a synth arpeggio, a drum pattern. Compared with the pedal it is an idea in motion, but it has the same hypnotic effect.
In production
- Trap and rage: 808 static on the tonic (A in A minor) while the pad moves through Am – F – Dm: a modern pedal.
- Build-up: eighth-note bass on the dominant (E in A minor) rising in volume and filter.
- Arpeggio ostinato (A C E A) that doesn't change under different chords: it creates new colors at each change.
Real example
Bach's Prelude in C major BWV 846 (Well-Tempered Clavier, I) ends with a long dominant pedal on G followed by a tonic pedal on C. Ravel's “Boléro” (1928) is instead the rhythmic ostinato par excellence: the snare drum repeats the same cell throughout the piece.