What key/time signature is this song in?

[Bespinben]

Definitely 4/4 with approx. 100 quarters per minute

[Tobbeh99]

I think it's a 4/4. Don't know however if it's a slow q≈50, or a fast q≈100.

[Jompa]

Both kinda work, but I'd do 4/4.
In any case, it's definitely not a q=50. q=100

[Sebastian]

I also think 2/2 could work.....
It reminds me of a song I did once.....which was in 2/2.
4/4 works too!

[FireArrow]

Ok, thanks!

[Tobbeh99]

I've finished arranging this song but I don't know what tempo is most appropriate. Q approx 100, or a faster Q approx 200??
https://www.youtube.com/watch?v=xdFrlm-1U1k

[Sebastian]

Approx 100 for sure.

[Latios212]

I'm having some trouble with the timing in this one.

[Jompa]

4/4 swing

[mastersuperfan]

https://www.youtube.com/watch?v=ZnCof15XO6Y

This one is giving me a bit of trouble. First off, should I notate the beginning in 12/8 or 4/4 swing? And secondly, the tempo is right at 131 BPM in the beginning section for a dotted quarter if notated in 12/8 or a quarter note in 4/4 with swing. However, at 0:21, it turns into 6/8. This poses a problem: if I notate the part after 0:21 in 6/8, then I can't put in the precise tempo because 131 is odd. Any help? I want to keep the tempo consistent yet precise.

[FierceDeity]

Definitely not 4/4 swing. It's pretty rare to see swing without at least some reference to other jazz conventions, and this piece really has none. Also, if you already know it's going to be in a compound time (i.e. 6/8) later in the piece, it's pretty strange not to start that way, too, if that notation would work (not to mention, background strings start playing what would be triplet figures in 4/4 before then, anyways, so compound meter makes much more sense throughout). Though there's really nothing stopping you from putting the whole thing in 6/8; the difference between 12/8 and 6/8 in terms of accent patterns are even more subtle than those between 4/4 and 2/4. The reason 6/8 is more obvious for the second part is because the syncopation of the latter half of 12/8 would be much more awkward, but 6/8 still works just as well in the beginning.

TL;DR for the sake of cohesion and simplicity, I'd say go 6/8 the whole time.

As for tempo, I'm actually pretty confused as to your problem. Typically I round to an even number just for simplicity and because veeeeery few people would actually notice a 1bpm difference in tempo. But it doesn't seem like that's the issue you have with it; it sounds to me as if you think an original tempo of 131 wouldn't hold because of some change in pulse that would require a division of the tempo, but there is no change in pulse. Even if you started off in 4/4, (quarter = 131) would still carry over as (dotted quarter = 131).

As with most of my advice concerning metric notation, this can all be simplified down to this:
Y'all think too much. Occam's razor, yo.

[Jompa]

In any case, it would be preferable if the tempo marking actually is a marking on a metronome! For many actual physical metronomes not every single number of bpm are options. For the slow tempo marks it can sometimes be every ten or twenty, while the medium and faster ones usually differ by 4. So if you use a marking that's on metronomes that'd probably solve your problem. A couple of bpm doesn't make any difference for the listener anyways, and no one will even play it exactly as that in the first place.

Also, I'd personally put 12/8 instead of 6/8.

EDIT: And btw: It doesn't change time signature at 0:21, it's the same as it's been up to now.

EDIT AGAIN: And the tempo isn't changing either.... so dotten quarter=131 is still correct here.. EDIT AGAIN: (which is what Fierce is saying..)

[mastersuperfan]

The problem is, using either 12/8 or 6/8 for the entire piece doesn't really cut it. While technically having the same tempo in terms of the notes themselves, the first section in 12/8 is not identical to the second section's 6/8. Should I keep it all in 12/8 with the same tempo, then the second section would be expressing 6/8 measures in 12/8. I can't really explain it that well, but I wouldn't use the same time signature and tempo combination for both of them.

EDIT: @Fierce, if I were to use 6/8, then yes both parts can accommodate 6/8, but one technically has a compound meter twice as fast. Therefore, I'd either have to change the time signature, the tempo, or just have one section just be notated in a different time signature, which makes it awkward.

[Jompa]

But it is the same throughout!! 12/8 q=131 all the way is completely correct! 6/8 q=131 all the way would also work! Those two sections of the song aren't different in terms of time or compound meter at all!

[mastersuperfan]

I'll provide my arrangement so far to show this.

https://www.dropbox.com/s/61plufhfrrf2d47/Reaper%20Fortress.musx?dl=0&s=sl

As you can see, up to m11 everything is in the first section, arranged how it should be. Afterwards, while my issue is noticeable in the left hand, it's much more prominent in the right. Take a look at measures 15, 16, 19, and 20. The last three notes of each measure are forced to cross between the strong beats in 12/8 when in reality they are actually on the last three beats of a standard 6/8 measure. I hope this explains the problem.