Tutorial: How to do MIDI dumps

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Ok so I did all that and now Im working on new song with different sounds in multi single mode. But now when I want my old song back I load my sequencer but it now just plays sounds from new song arranged into old song. Im obviously not saving it correctly, I have been trying for two weeks to figure this out and I still dont get what Im doing wrong. Im following the steps that everyone is telling me but perhaps Im not doing correctly or something.

I am working with an akai mpc2000xl sequencer. When Ive finished my songA which Ive created with the virus indigo11 in multi single mode using 16 parts ,I want to save all the sounds exactly as they are then work on a new songB with different sounds once again in multi single mode using a different 16 parts.
So what I want to know is firstly how to store everthing exactly the way it is in the virus for songA then how to recall it if I want to work on the songA again later. I have done everything people are telling me and it does not happen. I just get the same songA arrangement but it plays the sounds from the current multi single the new songB, of which the part names and numbers are showing on screen as this was the last thing I did.
Do I need to dial the 16 parts from songA back in manually later if I want to use? This means I would have to remember or write down the numbers so surely this is not the way to do it.
When I press store in multi mode, what does this actually store and where? My understanding is that it stores the 16parts Im using in multi single in the order in which they are arranged. So how do I recall that later?
If I press store in multi single mode I understand that Im storing a single sound of which I may have changed some relevant parameters and effects etc. So its not much different to single mode? I lose whatever was in its place by overwriting it. Is this correct?
This seems impractical. Why is there not an empty memory bank to store stuff? Can I save original sound somehow before changes?