nl553 -
Ok. I still didn't really understand what exactly is it that you're doing, but I'm going to review with yuo some basic procedures.
After you record the drum machine (which I presume, you're ok. with), most people record a bass line, or some basic chords (guitar, keyboard, etc.). Vocals usually come in last, or towards the end. If you only have four tracks, I presume one would be used for the drum beat, one keyboard track, one guitar track and one vocal track. Correct me if I'm wrong.
After you have a beat reference (drums), and a pitch reference (keyboard), you are ready to record the vocals. When setting the gain (volume) for your microphone, watch the level meter carefully. The optimum gain (with analogue tpae, that is), is achieved when the meters hit the red zone only during your loudest parts. During "Normal" parts, it should read at -5 or something of a sort. Recording too loud would result in distortion, and too soft would result in a noisy signal.
After you have your four tracks done, you should start the mixing process (give yourself a bit of a rest before you start. Your ears are still tired from recording). First get the drums and vocals to sit well together, then slowly add the other parts. Always watch those meters, that should not hit the red too much. If they do, this is where the master volume comes handy. If you mix-down to your computer, watch the computer's level meter carefully, because when recording to digital, once you hit 0dB, (Red), even for a second, you're toast. If you're mixing down to tape, don't worry about it too much.
This should get you started. Hope I helped.
Now go and record something!
Oren