Virtual piano

Tap or click a key to play it, or slide along the keys with the mouse held down. On a computer the keyboard works too: the bottom row of letters, Z to M, plays the lower octave and the top row, Q to I, plays the upper one, with the black keys on the row above each. Press several at once and they sound together, so three fingers make a chord. The minus and equals keys move the keyboard down or up an octave.

The chords of a key. Pick a key and its seven chords appear above the keys, each with its Roman numeral: I for the chord on the home note, IV on the fourth, and so on. Tap one to hear it and watch its three notes light up, then find the same notes yourself.

Chord mode. Switch to Chords and every key plays the chord built on it instead of one note. It uses the chord that belongs to your key, so in C major the D key plays D minor and the G key plays G major; a key outside the scale plays a major chord.

Progressions. Under the keys, each common progression plays its chords in your key, one after another. Its own page has the same chords with drums, bass and a style around them.

What you just heard: chords of three notes, each a note apart in the key. I–V–vi–IV puts four of them in a loop, and piano stabs are the house way of playing them, short and off the beat.