Akai MPC Reference Manual page 61

Next to the send effects, you have access to 8 submix dials which
control the volume of the corresponding submix channel. In the
Program Mixer, you can route the audio signal to the desired submix
bus. Please read more on this on Page 57.
Below the Submix section you can find additional master insert effects.
These can be used to apply effects such as Compressor Master or
Transient Shaper to finalize your entire mix. Click on the arrow of the
slot you want to assign an effect to. A pop-up menu lets you choose
from a palette of various effects, which can be loaded directly. Click on
a loaded effect name to open its graphic user interface for more
detailed editing.
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