[Guide/Discussion] Using Unsupported Beat Snap Divisors

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Topic Starter
Disclaimer: this “technique” has been known for god knows how long by more experienced timing people but i couldn’t find “good” documents of it, therefore I thought it would be nice if this knowledge was more common. Most of this was written for the sake of mapping discussions, although if you’re *only* interested on how to do it, skip to the "Tutorial" section.

If you wanted a more informal and memey version of this, here's the original document:

There has been a few instances that weird snappings have cropped up lately, some examples on top of my head:

Probably a few more and probably sometimes completely ignored or approximated in one way or another. This is more often present in some other genres that aren’t popular on osu! yet such as prog rock/metal, jazz, etc. Also performances by virtuosos, if we ever lose our sanity to map that stuff.



How the mapping community regards snapping in osu is largely influenced by the use of the “Beat Snap Divisor” thingy in the editor: 1/2 , 1/3, 1/4, 1/6, etc. This leads to the use of things like 3/2 or 2/3 or 3/4 (x/y) to indicate rhythm patterns like those:




This is pretty intuitive because you use the 1/y divisor then just place a note every x tick of that divisor. For example, to make a 3/4 rhythm you just need to change your divisor to 1/4 and place a note every 3 ticks.


“Ok but the piano plays a 2/5 rhythm.”
“Yea that’s just one place, a bit later it plays a 5/24 rhythm.”
“5/ what”

Right, probably about 1000 songs you come across you would only encounter one of them being this weird. However, it is a valid and well-documented use of rhythm in music when you mix two rhythm patterns that are not easily perceivable altogether. It is called “Polyrhythm”, but I prefer just calling it “weird snaps”, less pretentious.

Orange lines are where the notes are synced on beats

A simple case of this is the guitar playing 1/3 while drums doing 1/4 and the two instruments would sync notes every 1 beat.

Orange lines are where the notes are synced on beats, red are beats where notes are NOT synced

A more complicated case of this is the guitar playing a 2/7 while drums doing 1/4. The instruments would sync notes every 2 beats.

From those two examples you can probably tell how weird and awkward things could turn out if the songwriter decides to spice things up. I don’t want to delve deeper into polyrhythms since I’m not an expert in music but feel free to look up stuff like this it’s actually quite interesting.

Side Note

It could be slightly overwhelming to see really irregular fractions like 2/5, 5/24, 3/17,etc. but if you think of 5/24 as “24 notes over 5 beats” then things become a bit easier to comprehend. Or 12 notes over 2.5 beats, or 6 notes over 1.25 beats.

After 24 notes and 5 beats the rhythm pattern is complete and is again synced with a beat.


Consider this formula:

where BPMₜₑₘₚ is your temporary BPM, BPM₀ is your original BPM, Divisor is the beat snap divisor supported by osu that you use with the temporary BPM to snap notes to and Snapping is your actual snapping in the original BPM.

This is essentially a conversion formula changing a snapping to another at a different bpm. A simple case is how fast is a 170bpm 1/6 stream in 1/4 beat snap divisor. The answer is:

So it would be as fast as your “255bpm streams” since the osu! Community is too accustomed to using 1/4 as a measure of streams. This is a commonly known result as a sanity check for the equation.

This can be used to convert unsupported beat snap divisors. Say you want to snap your notes to 1/5 using 1/4 divisor:

Then in the editor, follow these by steps:

1. You zone in the place where the 1/5 snaps happens by placing 2 redlines: one at the start and one at the end of the 1/5 section.

2. Change the bpm of the first line to the calculated temporary BPM.

3. Use the divisor (in this case 1/4) to map the weird snaps. Calculate what the slider velocity should be to be equal to that of the original BPM:

where SV₀ is the SV multiplier at the original bpm. For example, if your SV multiplier in that section is 1.2x then SVₜₑₘₚ = (170/212.5) x 1.2 = 0.96 .
Apply this SV multiplier to the 1/5 snaps section using a green line.
Note: this only matters if you use sliders, if you map circles then you don’t need to worry about it.

4. Delete the redlines you’ve placed in step 1 as well as the green line you’ve placed in step 3. It is best not to drag those notes on the timeline since it will ruin all the hard work you've made so far. If you need to touch those to do anything like hitsounds or nc-ing, click the “Lock Notes” button on the lower right corner of the editor.

The AIMod will complain about those notes being "unsnapped". However, rest assured that they are since AIMod cannot detect unsupported snappings on its own. It is a useful tool to find snappings like those as a modder however.


1. So how do you snap things like 5/24 then?

You can either:
Convert using the temporary BPM formula from 1/24 to 1/6, then snap notes to every 5 1/6 ticks.
Just convert 5/24 to 1/6 then just snap notes to every 1/6 ticks.
I prefer the latter method, it’s just more efficient and foolproof.

2. ...This seems so complicated, do we even need this?
Good question.
This is mostly applicable to things that are intentionally written in the song. Look for repetitions in the song, if this happens a lot (at least more than once) or the music literally stops for this complex rhythm pattern to shine, then this would come in handy.

On the other hand, if the intention isn’t so clear: “5/24” guitar along with 1/3 drums at 300bpm, then it’s much better to snap to the drums because the “5/24” could very well be either: 1/6 (4/24) or 1/4 (6/24), because 5/24 is literally in between those two and it is most likely because the guitarist wasn’t being consistent.

Tough calls and sometimes simpler approximations would result in better gameplay. However, if you can successfully exploit clearly intentional complex snappings into gameplay it would make the map much more engaging and interesting. This requires experience, a good pool of testplayers who are capable of reading something more complex than generic rhythms and of course your own judgement in difficulty design. I’d like to see more complex rhythms and snappings being something seen more often in the ranked section as it is certainly not just memorising but also part of reading and finger control skillsets.

3. Why don’t you just use the temporary BPM and leave it there, is deleting those redlines absolutely necessary?

“Whatever works”, probably my motto for timing since it is definitely more subjective than it seems for a lot of people.
It is mostly fine if your set is a single diff since nothing else but that diff matters. Things get a bit more complicated when you have a set and you just simply can’t afford to follow those snappings on lower diffs. Either that or a gder has a better idea of mapping that part without following those snaps. That’s when you don’t want the bpm to change since the bpm of the song does not actually change, again, it’s just “weird snaps”.

4. Does the “divisor” value actually matter? I can just choose 1/3 divisor and get a different temporary BPM value and can still snap accurately.

Yea, you are kinda right. It doesn’t really matter if you know what you’re doing. However, it helps with things like grouping sometimes and gives you a better idea on how to group beats. Let’s say the 5/24 is recommended to be converted to 1/3 or 1/6 snap divisors since 5/24 streams tend to go in groups of 3s (or 6s) like swing rather than straight beats (2s, 4s, 8s) like 1/2 or 1/4.


This only concerns a very small percentage of songs that are mappable on osu but that doesn't mean it should be neglected. I hope this somehow encourages mapper to incorporate more interesting snappings in gameplay while being fitting with the song. I also didn't mean this to be a reference for disqualifications regarding simplifications especially when the mapper has a valid reason not to map it, it is simply a tool you could use if you wish to design your map with complex snappings.

Feel free to leave your feedback and correct me if I am wrong.


edits: typos
Great writeup!
Smug Nanachi
In mania, this technique is used a lot to create dump-styled maps, where the mapper artificially increases the difficulty by mapping to non-existent sounds to capture the "feeling" of the map better. There should be a documentation somewhere, but I don't know

An example of dump using this style
( which used a lot of 1/5 snaps to represent 1/4 rhythms
Topic Starter

AncuL wrote:

In mania, this technique is used a lot to create dump-styled maps, where the mapper artificially increases the difficulty by mapping to non-existent sounds to capture the "feeling" of the map better. There should be a documentation somewhere, but I don't know

An example of dump using this style
( which used a lot of 1/5 snaps to represent 1/4 rhythms

Yea it's not unheard of to create maps with made-up snappings, especially taiko or mania. Each game mode has its own terms: overmapping (or a more positive (or sugarcoated?) version, "additive rhythm") in std, improvisation(?) in taiko. I am not surprised by the mania community since they have a much longer history than std (or maybe even taiko?).

The idea of changing the bpm to something you could snap was indeed present for a long time, I just wanted to compile a few things and made the approach more methodical, or "good practice", I'd say, to prevent annoying shenanigans like SV being messed up or timing is not applicable for other difficulties in a set.

I also wanted to say that snappings like those actually exists in music even if rarely and if the mapper wanted to follow that they've got a tool to do so.


Edit: Noted and Bookmarked!!!
Hi youtube.
the fact that this isnt the guide to slap chicks disappointed me
agree with scub, a real-life skill such as slapping chicks would be way more useful
Topic Starter

ScubDomino wrote:

the fact that this isnt the guide to slap chicks disappointed me

sorry for bamboozle
Thank you so much.
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