i heard you can have a pad playing and record with ext. source on at the same time...when you do this does it record both sounds together or does it just record what i made with ext. source on to a seperate pad then i must resample both pads together?

it's just resampling but you can turn the ext source on while you are doing it, so yes, the sounds get mixed together, which is what you've been asking about, the difference between this and having the 2 sampler combo is that with the 2 sampler combo you can record in the external source and still have it seperate on its own pad and can mix it or chop it up and rearrange it afterwards

you would need to buy a 303 do this 'resampling with the ext source on' trick anyway seeing as you only have a 404, so if you got one, you would have all of these options to choose from