Not Sure of what knowledge you already have of Rhythm and wouldn't want to patronise but heres my Mathemagics and wisdom from almost 20 years of sampling and dancing not to mention a few years of Astronauticimizationalismal Philosophy (spell check didn't get that one

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Quantisation is Fractions of a bar at a given Time Signature say 4/4 in most cases , 4 beats to a bar , with 96 pulses per beat.
Tempo is actual time relative to total Beats Per Minute (obviously you say) , but the theory of time signature helps to universally divide the maths of rhythm independant of how fast or slow it may be played !!
MPC Recorded Sounds played at original pitch and time are made up of tiny fractions of points plotted in a kind of bar graph forming a digital waveform at the rate (in this case of 1 point (actual sample) per 0.0226757millisecond (ms)
Most sequencers use 96ppb (pulses per beat) (Or Clicks per beat) So if you have software sequencer with sample edit you can analyze sampled drums ... using zoom you can see where the peaks are in existing audio ... take a couple of famous breaks and write down the drum placement with the amount of clicks ... you will soon notice that drums vary a lot from bar to bar but still sound good ... Good Drummers Juggle the swing and balance between late and early , ahead of the beat and behind ... Ableton and Fruityloops etc have these called "grooves" and logic too now "I think" (I'm still with logic 5.5 PC , so not sure about new sequencers;)))) But grooves is what its all about Or The principal of groove/swing. I like to think of fat Arses !! who doesn't ?, but Fat Arses Bounce with a certain ratio of swing dependant on weight ... Swing is the same .. for every Action an equal opposite reaction ....Or Boing diddy Boing diddy diddy Boing diddy Boing ... Things always balance out .
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But all this depends on how your drums are chopped ...
Prefade (the distance from the start of the sample to the peak volume of the wave)
... hard sounds generally have a short prefade ...
If you are familiar with logic audio then you will/should have used the Start Point marker , you slide this to the peak volume of the sample and this is then the point aligned to time in the sequencer , I mean it is a way of ignoring the prefade and just quantizing/arranging by volume rather than the very start of each sample...
You can do this on MPC too with a lil' patience...
If every sample you use has a prefade of 5000samples (113.38mseconds or 0.113 of a second) then all volume peaks will be in sync !!
This does mean you will have spend a little time adding a silent section of sample to the start of every sample in your drum kit ... but really pays when layering drums .. you have to use the INSERT SOUND/SECTION START in EDIT ... I usually have a blank sample of 5000sample length as my first sound in my sound list (easier to find) I measure the samples of the existing prefade of the sample I'm working on (making a note of that number) and then INSERT the blank sample at the start ...Then discard the same amount of samples (that I made a note of) from the newly added blank prefade.... Now the sample has a 5000sample prefade regardless of its audible prefade ..
Just reading that back sounds confusing as hell, but its correct.
I guess you could just say... Add blank samples to the prefade until the prefade equals 5000 samples .... this way all samples sound synced and amplitudes peaks will match up .
So I like the Prefade to be 5000samples and I know where my Peaks are ... Oh yeah that brings me back to Fat Arses .... Skinny ones have no bounce too tight is like hearing a wack dinosaur beat !!!

Funk is precise swing !! Not robotic machine like hypnosis !! Some people escape in a trance and some people make joyful sounds to relish / realise the moment ... seems like some people don't live it up ! More Die off ! The family tree is an interesting thing With Juice In the Root, Funk in the Trunk, and Branches to Leave by

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So thats how to get everything synced , but when analysing famous drums you should notice that things don't always match up but often (for example) the HiHat happens just before or after the snare and rimshot later ... making for a fatter amplitude peak and fatter sound ..
Well however you prefer to play drums at least you can have control over the prefade length with accuracy ... Its true a lot of drums sound nice with prefade chopped off but some need it ... a mixture of the two is sweetest .
The MPC2000XL and well all digital equipment struggle with sharp attack or decay .. you will have noticed that samples don't play to the very end ?? Very small files don't even sound at all , well this is the Amp Attack Release Hardware capabilities tied with processor speed .... to get small files to play on the MPC then add a Postfade (long bit of silent sample to the end of the file/sound ) ... this is another good reason for adding Prefades as the Natural Audible Prefade of any sound is able to be heard.
Beware of making these Pre/post fade silences too long as you won't be able to use the variable ATT/DEC in the program section of the MPC
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BUT back to your original question of STEP EDIT
Never have a Rhythm on the exact quant point !
Always make Every Bar different !
LISTEN to good MUSIC and hear what happens at the very point of nodding your head or tapping your finger and notice that Good Music generally has an IMPLIED Beat but surprise and suspense of actual sounds heard .. NOT a BLATENT PATRONISING RHYTHM LIKE 'Military Marches' !
Keep it a Human feel like real drummers !
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The ZONE window works as a grid to measure by ... Not just for cutting up !!!!
Viewing at 12 zones on 1 beat is cool as it covers most cases and you can easily identify ,triplets, 16ths , eighths and up to 48ths , its also obvious where 96ths fall between the lines .!
Heres some Maths for you:
96 divided by 16 = 6 or...written like this
96 /16 = 6
96 /12 = 8
96 / 8 = 12
96 / 6 = 16
96 / 4 = 24
96 / 3 = 32
therefore if you chop a 2 bar break into 16 zones each beat chop will be exactly one beat , "obviously" ( i hear u mutter) but if you then press ZONE again on one of those One Beat samples you will see that 16 zones over a One Beat sample helps you analyze exactly where drums happen in breaks or other good rhythms of interest ..
So 16 zones over 1 beat is 6 clicks per zone, or..
16/6 Good Accurate viewing of swing each fraction being 6 clicks.
12/8 And thats a Quant setting of 1/32 (3) each fraction being 8 clicks.
8/12 And thats a Quant setting of 1/32 each fraction being 12 clicks.
6/16 And thats a Quant setting of 1/16 (3) each fraction being 16 clicks.
4/24 And thats a Quant setting of 1/16 each fraction being 24 clicks.
3/32 And thats a Quant setting of 1/8 (3) each fraction being 32 clicks.
2/48 And thats a Quant setting of 1/8 each fraction being 48 clicks.
1/96 And thats a Quant setting of OFF every/any click possible. (Realtime..ish)
(So.. the left number eg. 16 is the amount of zones to set in the ZONE window and the right number eg 6 is the amount of clicks in Step Edit )
so when i say 5000ms thats assuming you are on the MPC2000xl which has 44,100 hz per second sample rate,
Thats 44,100 Samples a second .
So if 1000 miliseconds is 1 second,
44.1 samples in evey milisecond ,
(1/44.1 = 0.02267573696)
0.0226757ms per sample
0.0226757ms x 5000smp = 113.3785 (0.11second) ideal for drums

JZA