MPC ISSUE - Sounds Keep Changing

I'm new to the mcp. I've always wanted one and now i got one, well a studio but its close. now my issue is as stated. how do you record your song right? example. i use plugin to create a melody. now i wanna lay drums on it. but when i switch it back to drums it just changes the sound of the whole melody. instead of keeping the melody and now letting me add drums to it. is it or does it have something to do with programs,tracks and sequences. now with the mlc everything has to be done manually I'm guessing. i can just record few drum sequences let it play and add as i go? when i try to do so it just overdubs my melody i created using the bank. and the sounds become whatever i have on the playing pad. what am i doing wrong. id like to construct atlas one beat please help. I'm a true beg in this mlc world . plan on buying the ebook, but for now id like to tackle this issue like this.

https://www.youtube.com/watch?v=kZIduIkYNes

This should give you the very basics.

I've seen this already. it goes into detail but it doesn't really answer my question. trust me I've searched high and low. and I'm going to continue.

Each instrument needs to go on its own track, so if your plugin melody is in track 1, press the TRACK+ key on the studio and assign your drum program to this track. Now record your drums.

MPC-Tutor wrote:Each instrument needs to go on its own track, so if your plugin melody is in track 1, press the TRACK+ key on the studio and assign your drum program to this track. Now record your drums.

Having same issues however each instrument i used is assigned to its own track , all relevant tracks, instruments & presets saved & worked fine until software crash & upon reboot it had not only changed the sound but also changed all saved input channels etc. Very frustrating