That function is in the mixer somewhere. I'm sure I have seen it. Press DIRECT ACCESS then the part you want to change (Main, Layered, Left) and you will be in the digital mixing, tune section.
It took me a about 10 days before I could take the keyboard out to gigs. When our baby, born premature, was in the hospital and she would sleep 90% of the time when we would go to visit her, I would bring the PSR2000 manual and study its sparse and sometimes cryptic explanations of the keyboard's functions. This helped a lot. I really recommend reading the manual carefully. I also highly recommend pressing the DIRECT ACCESS button and then all of the other buttons to see what shortcuts are available.
To set up the PSR2000 for gigs, I recommend that with your favorite floppy styles you save them to the desired tempo and also the desired OTS including multipads, left voice, DSPs, voice volumes, multipad volume, left hold, etc. To save an OTS, you press MEMORY>OTS 1,2,3, or 4. You are asked if you want to save the changes. If you set OTS 1 and want to work on OTS 2, you can press NO, and wait until you have set all four OTSs. Then on the last one you press MEMORY>OTS 1,2,3, or 4, and select YES. Then you save the style either on the floppy drive by pressing NEXT and SAVE or on the USER drive by pressing save. You will be informed that this style already exists and if you wish to overwrite it. Press YES.

You should also dedicate 1 registration button to adjusting your global settings. This keyboard doesn't automatically remember your global preferences, like mic reverb, vocal harmony type, mic volume, pedal functions, etc. So get the keyboard set up the way you would want it when you start your show. Then press MEMORY>REGISTRATION buttons 1-8. After you press memory, you should select the settings you wish to be remembered. To save the configuration of Registration buttons 1-8, you have to save them to memory by pressing J (in the main screen) and then SAVE if you are saving it to user memory or NEXT and SAVE if you are saving it to floppy. Then you can create a name for your registration. Before you start your show, you press
1. J
2. The registration that has your global preferences.
3. The button that calls up your global preferences.

Now you can select your style of choice, adjust tempo and transpose, press the OTS of choice, quickly press the right buttons to trigger the style, and you are ready to go.

If you use a lot of floppies, having a plastic case of floppies velcroed to the side of the keyboard is very helpful.

Other setup tips might have to do with your particular approach to music. Even though the PSR2000 has some disadvantages compared to the PSR740, the keyboard is overall much much better. There are too many ways that it's better to go into. I only wish it were better in every way. I don't know why Yamaha would go backwards in certain features.