In Melodyne you use the format tool to change the timbre of notes. You might be able to get something close to the original timbre, however 6 half tones is a lot jump so you may run into other artifacts.

But the real question is how good is your friends hearing? The reason I ask is because even though you can move notes around they will not sound exactly like the original note. Each note has a specific set of harmonics/formats. When you move a note those harmonics/formats move the same amount as the original note while the destination note will have a different set of harmonics/formats.

BUT only a few people will be able to tell the difference. I worked with a guy whos daughter sang a wrong note so I moved it to the right note one step higher. He could tell that wasn't sounding right; he had no idea what I was doing while using Medodyne. Personally I can not tell the difference.

I just posted a selfie and all of the responses were get well soon!

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware