A piano/keyboard is your best friend. For your tracks, instead of having loads of instruments, just have a piano, your melody (vocal?) and some percussion. Maybe you could use a drum loop and the groove of it will help you shape the rhythm of the melody? If you already have the melody in mind, lay it down if you can play it into a controller keyboard. If you haven't got one, go buy a cheap one; it's far easier than using a mouse. Then make a drum or perc pattern that goes with it.
The key thing is building it up with the detail last. On maybe another track, get some chords that fit under the melody. The strong beats in your drum/perc part may help you decide where to change chords.
If it's sounding good at this point and only then, you could separate out individual notes from your keyboard harmony and give them to other instruments. Worry about things like sampler patches and effects very last thing.
An old trick to adding harmony (specifically called 'countermelody') is copying the melody to a new track (and intrument), putting the entire thing up four semitones OR down 8 semitones, perhaps using the Matrix editor? Most of the time, these notes will fit as harmony.
Bass lines are perhaps the most important aspect of harmony. Unless you know about inversions, put the lowest note (bass guitar, synth, whatever) as the lowest note of the chord you're in and don't change it anywhere near as often as the melody. When to change it? You'll need to know what chord you're already on, then make it the root of it (e.g. for A minor, use A).
There's no two ways about it, you'll need to know something about theory to make harmonies work. Imagination is important, and you're in the best position to make it work because you'll know the style you want.
As for me, I'm a nerdy student with nothing better to do!
Percy
