Notes

The arrows placed in all of your song's charts are called notes. Depending on the noteskin, notes can have different colors depending on what beat the note falls on.

Most SM versions support up to 192nd notes, or 64th note triplets (3.9 does not have a standalone 192nd snap however), but depending on what custom build you are using, the note threshold may be higher.

4th note (1)
This note appears in almost every chart, and is the most common note used in every chart. Most beginner charts use only these notes. In most noteskins, this note is usually colored red in NOTE or orange in RAINBOW.

8th note (1/2)
These notes fall on half a beat, and usually start appearing in Easy/Light/Basic charts. In most noteskins, this note is usually colored blue in NOTE or cyan in RAINBOW.

12th note (1/3)
These notes fall on one third of a beat and are usually used in 3/4 time songs. (4th note triplet) In most noteskins, this note is usually colored purple in RAINBOW or green in NOTE.

16th note (1/4)
These notes fall on a quarter of a beat and usually start appearing in Medium/Standard/Difficult charts. Usually used in gallops and trills. In most noteskins (except in DDR's RAINBOW noteskins), this note is usually colored yellow in NOTE.

20th note (1/5)
These notes are 192nds at different intervals (10-10-9-10-9) which can be added in ArrowVortex. In ArrowVortex this note appears grey and a steady 20th pattern goes like this: red-grey-grey-grey-grey.

24th note (1/6)
These notes fall on 1/6 of a beat. (8th note triplet) Used with 12ths to form gallops or trills depending on the rhythm of the song, and appear on harder charts and a few medium charts. In most noteskins (except in DDR's NOTE or RAINBOW noteskins), this note is usually colored pink or purple.

32nd note (1/8)
These notes fall on 1/8 of a beat. Unless the song has really complex rhythms, these are usually used in slowdown sections, played as if they were 16ths at normal BPM. In most noteskins (except in DDR's NOTE or RAINBOW noteskins), this note is usually colored orange.

48th note (1/12)
These notes fall on 1/12 of a beat. (16th note triplet) They are very rare to find in most normal paddable charts. The only real uses for them is for really close sounds or 24ths at half BPM. In most noteskins (except in DDR's NOTE or RAINBOW noteskins), this note is usually colored cyan, pink, or purple.

64th note (1/16)
These notes fall on 1/16 of a beat and are used for swing rhythms, or really slow slowdowns. There's not much use beyond those uses. In most noteskins (except in DDR's NOTE or RAINBOW noteskins), this note is usually colored green.

96th note (1/24)
These notes fall on 1/24 of a beat. (32nd note triplet) To insert them in a simfile, use the 192nd snap and place a note every 2 rows. 96th and higher notes are not really used in any file at all, but most keyboard files use them to represent pitch changes, voice stepping, or just plain visual purposes. If you're stepping a file and you need to use a lot of them to keep the chart in sync, definitely check your BPM. In most noteskins (except in DDR's NOTE or RAINBOW noteskins), this note is usually colored green, gray, or white.

128th note (1/32)
These notes fall on 1/32 of a beat. In Stepmania AMX, this note is colored pastel blue. There are very few songs out there with 128th swing or 128th rhythms, but that can be accomplished in other SM versions by changing the BPM at these parts to make the notes play like 128ths. This custom snap can be approximated in other SM versions by spacing each note two 192nds, then one 192nd, then repeating the pattern.

192nd note (1/48)
These notes fall on 1/48 of a beat. (64th note triplet) To insert them in a simfile, use the 192nd snap and place a note every row. In Stepmania 5, this note is colored olive.

256th note (1/64)
These notes fall on 1/64 of a beat. In Stepmania AMX, this note is colored maroon. 256th rhythm songs are even harder to find than 128th rhythm songs, so this note is hardly ever used.

384th note (1/96)
These notes fall on 1/96 of a beat. (128th note triplet) In Stepmania AMX, this note is colored very dark cyan. It is extremely rare to find a song that would even need this type of note in it; even most keyboard charts need only up to 192nds to make something good.

768th note (1/192)
These notes fall on 1/192 of a beat. (256th note triplet) In Stepmania AMX, this note is colored grey. You probably won't ever need to use these in your song unless it's like 5 BPM and it would need a really high speed mod (like 100x or above) to read it properly.

4000th note (1/1000)
This note is exclusive to Rhythm Horizon, a 9-panel dance game which isn't affiliated with StepMania. There are probably no songs in that game that ever used this note, but a snap to add notes that fall on 1/1000 of a beat is somehow available in the Rhythm Horizon editor. In the Rhythm Horizon editor, this note is colored orange.