There is an option to interpret chords from a MIDI file, but I'm fairly sure that it requires multiple parts (bass, guitar, piano, melody etc) and therefore I'm not sure if a single note melody could be used successfully.

File > Import Chords > Import Chords from MIDI file (MIDI Chord Wizard)

From the integrated help:
"Import Chords from MIDI File (MIDI Chord Wizard)

Many people who play music by ear think of songs in terms of "Chords and Melody." However many MIDI files lack chord symbols, so they become difficult to learn without the user having to figure out the chords in a time consuming process. Now you can open any MIDI file in Band-in-a-Box, and Band-in-a-Box will automatically figure out the chords of the song for you. It automatically analyzes the MIDI file, figures out where the bass, piano, melody and other tracks are, and then figures out the chord changes for the song. The chords are written onto the Band-in-a-Box Chord Sheet like any other song. This allows you to quickly learn how to play a song from a MIDI file - just read it into Band-in-a-Box and you'll see the chord symbols, and then learn the Melody! You can also read tracks into the Melody and Soloist tracks."

BIAB & RB2025 Win.(Audiophile), Sonar Platinum, Cakewalk by Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Kontakt, Focusrite 18i20, KetronSD2, NS40M Monitors, Pioneer Active Monitors, AKG K271 Studio H'phones