Note values and rests

One whole note lasts as long as 2 half notes, 4 quarter notes, 8 eighth notes or 16 sixteenth notes.

Halving, again and again

Written music shows how long each sound lasts with the shape of the note. The system is built by halving. Start with the whole note, an open oval with no stem. Half of it is a half note, an open oval with a stem. Half of that is a quarter note, the same shape with the head filled in. Add a flag to the stem and you get an eighth note; two flags make a sixteenth note. Each step down lasts exactly half as long as the one above. The names in American English describe this division directly, while British English uses older names: semibreve, minim, crotchet, quaver and semiquaver.

Note values are relative, not fixed times. A quarter note has no length in seconds until you know the tempo and which note counts as the beat. In most songs the quarter note is the beat, so at 60 BPM it lasts one second, a half note two seconds and an eighth note half a second. At 120 BPM every one of those numbers halves. When eighth or sixteenth notes appear in a group, their flags are usually joined into thick horizontal lines called beams. Beams do not change the sound; they group notes so you can see where each beat starts.

Rests are measured silence

Silence in music is counted just as carefully as sound. Every note value has a matching rest. A whole rest is a small block hanging below a staff line and a half rest is the same block sitting on top of the line, which is easy to mix up; one memory trick is that the whole rest is heavier, so it hangs. The quarter rest is a zigzag stroke, the eighth rest a slanted line with one dot-like flag, and the sixteenth rest has two. A rest is not a pause in the beat. The beats carry on underneath, and you come back in exactly on time.

Filling a bar

Music in 4/4 is divided into bars of four quarter-note beats, and the values inside each bar must add up to exactly four. A half note plus two quarters fills a bar (2 + 1 + 1). So do four eighths and a half note (0.5 × 4 + 2). A whole note fills it alone. In the note blocks below, each button adds one value to the bars and the bar meter shows how full each bar is. If a value is too long for the space that remains, the lab refuses it and tells you what is left. Try filling the first bar three different ways before you press Play.

The Twinkle melody in the Tap along tab is an 18th-century French tune, known in French as "Ah! vous dirai-je, maman", and long out of copyright. Its rhythm is six quarter notes and a half note, twice: every second bar ends on a long note, which is what makes it easy to sing. Tap it with the sound on first, then switch the guide off and see if your timing holds.