Whole note
A whole note (in British terms a semibreve) is a hollow head with no stem. It lasts four beats: a whole measure of 4/4.
Play a whole note on “one” and hold it while you count to four. One sound, four beats. It is the longest of the basic values: one whole note lasts as long as two half notes or four quarter notes.
The other values take their names from it: a half note is half a whole note, a quarter note a quarter, an eighth note an eighth. You will not find a whole note in 3/4: it lasts one beat more than the measure can hold.
The whole rest lasts four beats and hangs down from the fourth line of the staff; the half rest sits on the middle line. The textbook’s way to remember it: the half rest sits, the whole rest hangs.
What it sounds like
A whole note sounds long and still, one stretched sound with four ticks of the beat under it. Pieces often end on one.
Where it is taught: the studio’s interactive textbook, chapter 2, “Counting: the beat, quarter and half notes”.