If I made vocal melodies on the top staff, does it have to be part of the specific chord progressions for each measure?
How would I make the melody on the top staff sound good from measure to measure while sounding good with the melodies on the bottom two staff?
Here's how I learned to write multiple melody lines playing at the same time:
If you stick with it and get all the way through the invention and edit and clean it up and play it and see that it sounds good, you will have basically taken a crash course in contrapuntal melody writing. Making multiple melody lines work together with an existing chord progression will be much easier after this exercise.
I sort of answered this in your last question. Any line in a particular bar must bear some relationship to the underlying harmony in that bar - the chord or chords.
There will be some notes which are chord tones, and passing notes which are not, but are often used on weak parts of a bar to get from one good note to another.
In your example though, there's another problem. You already have a 'melody line', so anything on top of that will also have to complement that line, as well as the chords.
One can make an argument that, no, melody & harmony need not be in agreement, but that all depends on the kind of sound you're aiming for. It took 500 years of Western Art Music history for Charles Ives to pull that off with any great success.
Ultimately the real test of what "sounds good" is a matter of taste (on the part of the listener) & the composer's ability to argue their case through their music. While in the general case of Western Music one would write a melody that worked with the exisiting harmonies & countermelodies, that may not meet your specific need, nor be what you hear as you write. Either way: you will need to practice arts of melody writing to compose a good tune.
& one can never go wrong studying counterpoint. After all: everything is counterpoint.
This particular example is Life on Mars? by David Bowie. The piano line does not double the tune, and it's not really a countermelody - it's just an outline of the harmonising chords using arpeggios rather than block chords. The pianist is Rick Wakeman.
As you want to write a new tune to the song whilst keeping the existing piano line, I'd suggest you analyze the chords being outlined (there's more going on than the guitar chords above the stave suggest!) and then construct your tune so its fits the discovered harmony.
