Your tascam machine, How many tracks?
Your mixer, How many channels? Ins & Outs?
Do you have a stereo buss on the mixer?
What I use to do with 4 trackers is record bass, drums, guitar on 3 seperate tracks.
I would then mix them to a buss and record them onto track 4
This would give me 3 seperate tracks for vocals, solo's etc.
It's not the best way to record instruments (all in mono) but it get's you by
and at the same time really get's you to really listen for relationships between the instruments and make sure they are working together.
Once you bounce a couple of instruments together you dont have control over them individually anymore.
Without knowing your setup, And how many instruments you plan to record. It is hard to determine the best path for you.
List out your gear and we can try to help you more.