1. Una Corda (una = 1, corda = string) - left soft pedal on a grand piano depresses the action so the hammer only strikes one of the three strings for each note in the treble and two of the three strings for each note in the bass.
2. Due Corde (due = 2, corda = string) - the center soft pedal on a grand piano lifts the action so the hammers strike two strings instead of three.
3. Tre Corde (tre = 3, corda = string) - no soft pedal depressed; all three strings sound.