Three dotted notes in 6/8 time signature

How many seconds will each note take in this 6/8 time signature, if tempo is 120 bpm?

My analysis :

Rest in the beginning will take three 1/8 beats - 0.75 seconds in total.

The three A note will take 3/2*1/4 = 3/8 seconds each.

Is this correct?

• There are no dotted notes in this example. There is a dotted rest, and there are three staccato notes. Staccato is indicated by a dot, but the staccato dot does not make the note a "dotted note." Apr 21, 2021 at 4:24
• It would be interesting to find out how one would time onself when playing the notes.
– Tim
Apr 21, 2021 at 7:13

The notes in your picture are not dotted notes, they are notes with staccato dots. https://en.wikipedia.org/wiki/Staccato

The dot that affects note length is positioned horizontally after the notehead. https://en.wikipedia.org/wiki/Dotted_note

• I've never understood why someone would write a dotted note (half as long again) as a staccato played note.
– Tim
Apr 21, 2021 at 7:11
• @Tim To notate the rhythm, why not. In my example here it doesn't make sense though, since after the dotted note there is a rest. But if it was an eight note, then it would make sense. Apr 21, 2021 at 7:18
• Since the staccato dot means shorten by roughly half, why not just write a note of that length instead. A player will make whichever note the appropriate length anyway.
– Tim
Apr 21, 2021 at 7:22
• @Tim Note length is not the same as sound length. Staccato modifies the length of sound, but not the rhythm. For example, if you first write a rhythm with dotted notes and without staccato. Then you write the exact same thing, but with staccato dots. It's the same rhythm, but to be played with short-sounding notes. Apr 21, 2021 at 7:40
• I understand that. What I don't understand is the difference between, say, in 4/4 four staccato crotchets and four quavers with quaver rests between.
– Tim
Apr 21, 2021 at 7:51

As Aaron writes, what a "beat" is is defined differently in different time signatures. Within regular time signatures (where every beat is the same) there are two types: simple and compound. Simple meters have beats subdivided into two parts each. Some examples are 2/4, 3/4, and 4/4. Compound meters have beats subdivided into three (usually) parts, for example as in 6/8, where there are two beats of three pulses. This is as opposed to 3/4 where there are three beats of two pulses. The general trick is to use an 8 in the bottom of the time signature when it would seem redundant (6/8 would mathematically reduce to 3/4 if it were actually a fraction).

So, in your excerpt, each beat can be assumed to have a length of a dotted quarter (crotchet). Since there are 60 seconds in a minute, 120 bpm = 2 beats per second, so an eighth note subdivision of one beat will take one-sixth of a second.

As a note, this is why tempo markings are often written e.g. ♩. = 120, instead of just 120 bpm, since that can be ambiguous.

The timings calculated are correct only if the beat is understood in terms of the quarter-note, which is unusual for sheet-music in 6/8 time, but typical for DAWs regardless of time signature.

The time depends on how the beat is represented. In 6/8 time, the tempo (BPM) is sometimes given in terms of the dotted quarter-note and sometimes in terms of the eighth-note.

♩. = 120

In this case, each beat lasts 1/2 seconds, and each eighth-note lasts 1/3 beat. Thus, the rest lasts 1/2 seconds, and each eighth-note lasts 1/6 seconds.

♪ = 120

In this case, the rest lasts 3/2 seconds, and each eighth-note lasts 1/2 second.

♩ = 120

Some DAWs always specify tempo in terms of the quarter-note, regardless the time signature. In that case, the rest lasts 3/4 seconds, and each eighth-note lasts 3/8 second.