Rhythm

Rhythm is the half of notation that says when and for how long. Get it wrong and the right pitches still sound wrong.

Two ideas carry most of the weight.

Relative duration

Note values are not fixed lengths in seconds. They are ratios. A half note is twice a quarter note, a quarter is twice an eighth, and so on down. Change the tempo and every value changes together; the relationships stay put. Note values covers the full ladder, including rests.

Grouping

A time signature tells you how those durations get bundled into bars: how many beats per bar, and which note value counts as the beat. 4/4 is four quarter notes to a bar. 6/8 is six eighth notes — usually felt as two groups of three.

The grouping is what gives music its feel. The same string of note values in 3/4 and in 6/8 are not the same piece.

Why this is worth drilling

Reading rhythm is a physical skill more than a conceptual one. You can understand dotted notes perfectly and still fall apart clapping them. Tapping exercises against a fixed pulse — which is what the rhythm games in Tomus are — close that gap faster than reading about it does.