Six-eight and three-eight
Count 6/8 in two beats of three and tell it from 3/4.
Two big beats
6/8 has six eighths, but it is counted not in six but in two: the eighths fall into two groups of three. The big beat is a dotted quarter note, and each divides into three eighths.
Meters whose beat divides into three are called compound. They sound "rocking": barcarolles, lullabies and jigs are written in them.
6/8: six eighths, two dotted quarters, "quarter – eighth"
The pulse of 6/8: ONE-and-a, TWO-and-a
Practice: Tap 6/8
Practice: A dictation in 6/8
6/8 is not 3/4
3/4 also holds six eighths, but grouped differently: three beats of two eighths. Compare by ear: 6/8 goes "ONE-and-a, TWO-and-a", 3/4 "ONE-and, TWO-and, THREE-and".
3/8 is a bar of three eighths, a single big beat. At a fast tempo it is counted "in one", like a quick waltz or a scherzo.
3/4: the same six eighths, in twos
The pulse of 3/4: ONE-and, TWO-and, THREE-and
3/8: three eighths, "quarter – eighth", a dotted quarter
Listen for where the accents fall. Two accents in a bar of six eighths: 6/8; three: 3/4. On the staff the grouping shows it: in 6/8 eighths are beamed in threes.