Need help adding bass-lines to melodies

[MultiScaleMale]

A chord progression would really help, but if you want to skip that step I won't try to stop you.

 

[MVE]

A chord progression would really help, but if you want to skip that step I won't try to stop you.

Yeah, the song has a chord progression whether you choose to play one or not.
So, I would recommend you find those chords, then build your bass line.

 

[Ekulati]

Interesting. A person knows a couple of mode names and their notes, but needs help adding a bass line (harmonizing, despite OPs disinterest in chords at this point) to an existing melody.

Maybe go back to around the 12th century or so and study how the first monophonic lines suddenly had a second line added below and became the earliest polyphony.

 

[tannis_root]

Maybe go back to around the 12th century or so and study how the first monophonic lines suddenly had a second line added below and became the earliest polyphony.

Ha! That's exactly what I intend to do! And/or that feels like where I am at. I have monophonic lines and now it's the 1700's and I'm going to add a second line to make them polyphonic.

There's a mnemonic which allows one to remember all the modes: "I Don't Punch Like Muhammed Ali". Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian. And Locrian. But I tend to think of everything as being varying degrees of Ionian. Numbers, not letters.