The original is *so* out of tune that autotune could only improve it. I agree that autotune is often noticeable on pop vocals, but that's because it's routinely overdone as an effect.

They could have cleaned up the bagpipe drones at the start a bit more.

Apart from the obvious re-arrangement, they also re-timed the drum hits, which sharpened things up a lot, but again only because it was so sloppy to begin with.

Autotuning like that needs each track to be recorded separately, either one at a time or with very good separation in the studio - otherwise an autotuned instrument will clash with its differently tuned bleed though another instrument's mic, making a very messy mix.

I don't recognise "Lament" as a morris tune - does anyone know where it comes from?