The askleo.com has this to say:

"Audio files contain actual sound recording while MIDI files are a type of computer program. Converting audio to midi is a nearly impossible task."

So much for that.

I have another idea. I have a Dear Husband who has a bass voice and is a virtual Gerald McBoing Boing. I'll invite friends over, let them play the melody, and invite the DH in to make the sound of a motorcycle idling roughly in Dm and 4/4 time. Everybody will have a good laugh, and we'll move on.

Thanks.