A metronome mark should give you both the tempo and the basis of that tempo, so the norm on music scores is not MM=xxx but [note value]=xxx

If a note value is not given - and it should be - then you need to look at the time signature to get the basis of the beat. For the common time signatures:

• 2/2 and 2/4 are two beats in a bar so a metronome mark (MM) is based on either the minim (1/2 note) for 2/2 or crotchet (1/4 note) for 2/4


• 4/4 is four beats in a bar so MM is based on crotchet


• 6/8 and 6/4 are two beats in a bar so MM is based on dotted crotchet or dotted minim respectively


• 3/4 and 3/8 are 3 beats in a bar so MM is based on crotchet or quaver (1/8th note) respectively.

you will also see C and C| (the | is through the C) which refer to 4/4 and 2/2 respectively.

You sometimes see reels and hornpipes notated with a 4/4 time signature. This is incorrect. As Jack says above they are in duple time and should be notated in 2/2 time.

Geoff