is there a way to do this so that i can layer things like keyboard/synth parts perfectly in sync and save time, instead of just record different notes and chords to different pads and replaying my melodies?

Use a sp303 or the 606(i think)
The sp303 can record the external source while resampling.

OR

Use an external sequencer/DAW and just time everything right and sample the external sequencer/DAW when done.

Sp303 resampling is the easiest and fastest way but won't match the flexibility of doing it with an external sequencer such as an mpc or a DAW like ableton live

i dont think the SP 303 can duplicate another sound while playing the pattern on the sp...even if you hit the source button and play.... how will you do it by resampling? can you explain that ?

okay i tried it and it worked on the sp... 1st resample something like a break loop....for as long as you want...then hit that resample/record and choose which pad you want to do your next layer with...build that way...i looked it up on youtube & other cats already explained before somewhere on here

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