The track mute and next sequence. These track mute is about the same as before. One big improvement is the ability to solo from this screen. This is probably the single biggest reason I upgraded. I loved using this screen but hated going back to the main screen and finding the correct track to solo something. Now its right there, by holding the SOLO [F6] and selecting a track (pad) to solo. Hit SOLO again to come out of it. One thing I do miss here is the ability to advance to the next sequence for this screen. Yes, this a big drawback. In order to advance to the next sequence you either have to go to the NEXT SEQ screen or go back to the main screen.
In the next sequence screen you do get a choice of immediately going to the next sequence or just waiting to for the current one play out as usual. Also in the NEXT SEQ screen you can select to go to PAD sequence selection. This is where you get Sequences displayed similar to the track mute screen and you just hid the pad that corresponds to the next sequence you want to play. Once the next sequence is reached that PAD selection becomes unhighlighted and you are ready to select the next one. (You cannot select two or more sequences to play here)
In addition to the dedicated NEXT SEQ screen you also can tell the MPC to switch sequences from external program changes to the channel you have the machine setup to receive (usually your master controller keyboard channel). This allows you to just switch programs on your controller and the MPC shows that to next sequence to be played. You can do this while the sequence is running or stopped. Unfortunately, this does not work in the TRACK MUTE screen (I had really hoped it would). Hopefully Akai with add this feature in a future OS. Switching sequences by program changes from a controller keyboard would be very handy with a foot pedal. Most controller keyboards can be set to advance through programs by footswitch. Imagine every time you step on the footswitch, the MPC advances to the next sequence, leaving your hands free to turn knobs on other equipment! Woohooo! (They could just add this to the already existing footpedal assignment screen there)
2nd sequence feature. You can assign a second sequence to be played with the currently selected sequence. This is not as much as it seems at first. All you get is to select one sequence to basically play 'in the background' for any sequence that is selected in the main screen. OK, an example would probably help. This is buried in the MISC screen but I don't know why. I go there and select SEQ-9 as the 2nd sequence. When I go back to the main screen, it indicates there's a 2nd sequence. I Start SEQ-1, and SEQ-9 will run at the same time. I switch to SEQ-3 and SEQ-9 will still be running, I switch to SEQ-2 and SEQ-9 will still be there until go back to the MISC screen and turn this off. I'm not sure why this feature is even there. I guess if you want to try different basslines with one sequence of percussion. I dunno.
Note variation slider. Some improvements here. Best I can tell, you can now just use it anytime, even while sequences are playing. I just assigned it to a note and to what value (no new values, just same old ones). Started a sequence and immediately heard results. I still does not affect the sample after it starts, so it still only gives the sample the new value before it plays (i.e. can't be used like a pitch bend). The note variation slider does not have to be recorded into a sequence to get used. This is nifty for real-time work on prerecorded sequences. You can also change what the note variation slider is assigned to when sequences are playing.