How do you know if a song has triplets in 4/4 or if the tempo is 3/4 ?
For example, consider this song :
For the first line ,
I can count 1,2,3 ,1,2,3 ,1,2,3 ,1,2,3
or simply 1 ,2 ,3 ,4
Does the song have 4 triplets or is it 3/4 ? I am confused as to how to find if a song like this is in 3/4 or 4/4
Technically speaking, you can't ever say for certain until you see the composer's original score (if there even is one); a piece could literally be written in an infinite number of time signatures. As such, we have to make these decisions based on a knowledge of prior practice and on what makes the most practical sense. So, let's look at this excerpt notated in the two manners you suggested:
Example 1: Notated in 4/4 with triplets
Well, that seems a bit hectic, doesn't it? Let's try this instead:
Example 2: Notated in (a fast) 3/4
Hopefully you agree that Example 2 is a bit more user-friendly than Example 1! Indeed, this alone should be enough to suggest that this was probably conceived in a fast 3/4, and this is not uncommon; though the individual beats themselves are quick, music like this is often felt "in one" instead of in three. So we don't feel it as a lightning-fast onetwothreeandonetwothreeand but rather as a more leisurely ONEtwothreeandONEtwothreeand. Thus I would bet that it was originally considered in a triple meter (as in, 3 on top in the time signature) instead of triplets in a duple or quadruple meter.
Edit: And here's another example to show what Tim discusses in his answer.
Example 3: Notated in 6/8
In my opinion, 6/8 is almost as good as 3/4, but 3/4 is still a little better. The left hand in m. 6 of Example 3 could definitely throw a sight-reader for a loop, whereas the same spot in Example 2 (m. 11) is as easy as it gets.
I'd put it in 6/8, due to the triplets feel, but the phrasing kind of repeats every two bars, thus two lots of 3/8, making 6/8. Why /8? Well, it's fairly quick, so I'd write it as quavers instead of crotchets. There is a recent question on that subject - quavers to play give the feeling that they are quicker - I know it depends on the tempo mark, but nevertheless...
It could be construed as 4/4, which may translate into 12/8, or could even be left as a simple 3/4, albeit a fast one.
A quick Google trawl sees it written both in 6/8 and 12/8 - intriguing?
In contrast to what Richard has written, I do not believe that this is in 3/4 time, and choosing a meter by which is visually easier (whatever that means) is misunderstanding what a meter really is. Meter is ultimately about what we can hear, and choosing a meter based on visual simplicity gives short shrift to our own ears.
In William Caplin's book Classical Form, he discussed real meter vs notated meter. The notated meter can not be determined by listening, whereas the real meter can only be perceived through hearing. As has been pointed out, this theme could be notated in many meters: 3/4, 3/8, 6/8, or 12/8. Heck, you could even notate it in 1/4 time, and the first doop doop doo-doo would take three measures. No matter how Ramin Djawadi chose to notate it, ultimately, what he wrote down is merely the notated meter, and unless one of us gets a chance to see his score, we will simply be guessing as to what that might be.
The real meter is also somewhat debatable, but there are some principles that we apply. Are these principles iron-clad? No. Nothing about real meter is iron-clad, but they are suggestive.
First, a measure should be long enough to carry a meaningful musical unit. This usually means that it carries more than a single impulse. This is the reason that I would reject 1/4, and suspect that 3/4 and 3/8 are both improbable as the real meter.
Then, we typically aim for roughly 8-bar phrases with 4-bar half-phrases. This is also a convention, but let us see where it takes us. 3/4 or 3/8 would lead to to 16-bar phrases. 1/4 would lead to a whopping 48 bar phrase. 12/8, however, with 4 triplets per bar, would bring us a 4 bar phrase.
This brings me to the conclusion that the most likely real meter is 6/8, which has 8 bar phrases, and measures that carry more musical material than a single impulse.
Now, as for the notated meter, that is a research question, and anyone's guess unless the composer or one of the players lets us know.
By total random chance, I have just seen a signed copy of the first page of Ramin Djawadi's score (!), and I can now confirm that the he notated it in 6/8:
You've almost answered your own question. At different time scales, different groupings appear: groupings of 3 ("is it in 3/4") within longer groupings of 4 ("is it in 4/4"), within even longer groupings ("is this two 2-bar phrases or one 4-bar phrase"). The composer has to choose one of these levels as the quarter note, just to be able to write it down. But a listener can pay attention to any of these levels.
For example, Liszt's famous Mephisto Waltz #1 (piano score and recordings easy to find on youtube) is notated as about 900 bars of 3/4, but counting 1-2-3 1-2-3 that fast is too exhausting. It's much easier to hear a "downbeat" on every fourth bar, or even every eighth bar.
