
I'm able to produce efficiently and find that "zone" we producers strive to be in. I'm able to do what it sounds like you're after. Last year I picked up an MPC and this time, it worked. Or maybe better said, producing by ear and touch rather than by sight and tone. I failed to follow through with the idea of "feeling" the music. But not because I chose machine over MPC. I first picked up the maschine when I was maybe 1 or 2 years into producing. It's not going to matter which one you choose.

I'm a bit biased because I own an MPC, but I don't think you can go wrong with the One. I can't remember the name of the software, but Ave Mcree has a YouTube video on the software. Yes, you can convert Native Instruments expansions to MPC. I've barely used Splice but it seems like a great resource for music producers. Splice is subscription based site that allows you to download a certain number of royalty free audio samples, midi files, etc. I watched so many YouTube videos on my MPC before it arrived in the mail that I was able to make a beat within the first hour of taking it out of the box. If you decide to get an MPC, purchase the MPC Bible - it's a digital book which walks you through everything in the MPC start to finish.

I'm a guitar player, but I've never used any music production software or tools. This is my first MPC and first device I've ever used for music production. I have an MPC Live 2 (which has the exact same operating system as the One and the same workflow).
