Pro's

Do most of the big producers sequence everything on the MPC or do they use something else?

that depends on what the individual is most comfortable with...
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seriously... if your a pro and your gettin' big checks... then your resources are abundant.... you can just wake up one... day and produce a beat using the triton for an artist... next day... you mess with the motif.... of you would always have one main that you will always fall back on to do most of your work..., but that doesn't mean your not allowed to explore and touch the other hardware/software pieces...