Akai MPC User Manual page 326

You can now add slice markers to a sample as it plays, letting you
edit easily in real time. To do this, click +Slice at any point during
sample playback.
Hardware: You can now add slice markers to a sample as it plays,
letting you edit easily in real time. To do this, press F6 (Slice +) at any
point during sample playback.
You can now quickly split or combine slices.
To split the current slice into two slices, click the + button to the right of the Slice field.
To combine the current slice and the previous one, click the – button to the right of the Slice field.
Hardware: You can now quickly split or combine slices.
To split or combine slices:
1. In Chop Mode, use the Cursor Buttons to select the Slice field.
2. Use the Data Dial or –/+ buttons to select the desired slice.
3. Press Window to open the Split/Combine Region window.
4. Press F4 (Split) to split the current slice into two slices, press F5 (Combine) to combine the current
slice and previous one, or press F2 (Back) to cancel the operation.
The Split/Combine Region window in Sample Edit Mode in the MPC hardware display.
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