It might be a stretch, but you could try recording your humming as an audio file, then put it through the Audio Chord Wizard in Band-in-a-Box so that you can send that info into BB to add the accompaniment (either keep or don't keep that recorded audio once you've sent the details to BB): https://www.pgmusic.com/manuals/bbw2024full/chapter11.htm#analyzing-chords-in-audio-audio-chord-wizard

(feature video, created in 2020)

-Callie