Differentiating between fast 6/8 and 4/4

Question

Take for (extreme) example, this song:

After half-time intro, the triplets on the double bass lend it a swaying six eight feel, but the meter can easily also be counted out in fours and syncopates a little better with the phrasing of the melody that way.

What are some of the methods of differentiating between the two when composing? At what threshold of bpm does this change in perception start to take effect? I realize the most of what's causing it here are the repetitious bass drum hits, which isn't a feature of most musical genres outside of metal, but the idea is applicable to any fast 6/8 meter songs.

Thanks!

Answer 1

You can't really differentiate between them. 4/4 is most often emphasized like this:

ONE two three four

6/8 like this:

ONE two three four five six

If you play triplets in 4/4 you get the exact same pattern as in 6/8. Similarly if you play dotted eighths in 6/8 you get the same pattern as 4/4.

In general you should pick a time signature for the effect it gives you when writing "naturally" in that time. What I mean by this is that "swaying six eight feel" you describe is related to having three notes per beat and more emphasis on the first beat per bar. 6/8 has three notes per beat by default, so you should use it if you want that effect rather than using triplets in 4/4, even though both have more emphasis on the first beat per bar. If you want two notes per beat, use 4/4. If you're going to have some mixture, use whatever makes it easier for you to write.

As noted in another answer, time signatures are arbitrary. Trying to differentiate between time signatures is futile because of how different people can perceive them, among other reasons. The change in perception you mention is different for everyone and many people won't even be aware of the time.

Your goal should be to produce the particular effect you desire, not to have a clear time signature recognizable to the listener. Time signatures are only a tool to make writing and reading music easier.

Answer 2

In the case linked above it's a fairly unambiguous 6/8 feel- even when it's punching along ridiculously fast it's still in clear threes, but often when it is a little more ambiguous you can think of it as being in 12/8, which a lot of people will tend to count as

one two three two two three three two three four two three

That is often the time signature when you have fours combined with a swung feel.

Answer 3

In that song, as you say, there are triplets on quarter notes of 2/4 or 4/4, or there is fast 6/8. You can write it both ways and get precisely the same music. The deciding factor is normally which way will be easier to read. If there are only a few triplets, then writing it in 4 would probably be better, and 6/8 might be better in a slower tune made up entirely of triplet forms.

In between? It can go either way. Who is your target "user"? Which will they prefer? If there is 2 against 3, which way will be more clear in the music? There is no definite right or wrong way. They are both correct, and you can use the one you prefer.

Answer 4

It's a slow 4/4 timing, BUT each beat has a sub-timing of 3.So, triplet feel on 4/4 gives a 12/8 time signature, quite common in slow blues numbers.If it might have been 6/8 there would be an obvious count of slow 2, which I can't feel.I could only listen for 90 secs though.

Answer 5

A good rule of thumb for deciding if it's 6/8 or 12/8, rather than 2/4 or 4/4 is this: If you can say "tiddly tiddly tiddly tiddly" along to it, then it's compound time (i.e 6/8 etc). if you can say "Tiddle tiddle tiddle tiddle" then it's normal time (i.e 2/4 etc).