Let’s say, for example, a songs BPM is 90. I could chart this at 45, 90, or 180. Either way my chart would be on time and accurate. Why Shouldn’t I do 45 or 180 or 90? To be proper, what should I do?

There are a few risks with charting a song at half or double the regular BPM:

– You have to remember to chart the BEAT track at half or double speed, or the player will see too many or too few beats in the background.

– The rule for sustains is 3/16th at regular BPM. At half or double speed, tools like CAT will apply the regular rules, and your sustains will be too short (double) or prematurely trimmed (half). The other reduction features of CAT will suffer similar problems: too many notes on EMH (double), or too few (half).

– The standard for vocal authoring is to use a 1/64 grid. If you chart a song at half or double speed, you’d have to remember to use a 1/128 or 1/32 grid. If you didn’t, the chart wouldn’t be accurate enough (half), or slides could be too short (double).

– If you don’t author all of the instruments, and someone else decides to continue your work, they’ll screw it up if they don’t notice the tempo is half or double what it should be.

TL;DR: Use the regular tempo.

Okay, so as far as deciding “regular”, I just need to argue with myself which BPM is more prevalent? And instead of going back and forth, leave the whole song at that BPM?

Does it affect the hitbox size? I’ve wondered that and so the only thing I can say ive ever done is try to change the BPM so that Im normally charting my drums with 1/32 grid. When the song picks up I double the BPM so my grid can stay at 1/32.

Don’t switch back and forth. Almost every song is between 50 and 160 BPM, and precious few have significant breaks where the BPM changes drastically.

I think the hitbox size is in milliseconds. The HoPo threshold in Magma certainly is.

I’m not sure what you mean by “when the song picks up” though. If the song is actually slowing down or speeding up, then change the BPM. If it’s just a change in the drum part, then don’t change the BPM. As a baseline example, there’s no significant change in BPM at the start of London Calling, though it “picks up” 20 seconds in:

http://youtu.be/KonmIMQelwM

No doubt 90ish. First thing to judge BPM: check the kick/snare pattern.

Thanks! Ill try to keep my BPMS lower from now on!

It’s not necessarily that they’re lower, but usually the snare/kick pattern will tell you the speed. A “normal” measure has 2 snare and 2 kicks (as a *structure*, not by simple count: a measure with a fill will obviously have plenty of snare hits).