The Challenge: Add an ad-hoc recorded acoustic track to an album of well-produced punchy symphonic metal without either overcompressing the acoustic song or dulling the majestic metal.
The Solution: The track itself was a quiet piano-and voice version of one of the main album tracks, with high dynamic range and a startlingly good performance. However, it was recorded separately from the rest of the album with lesser gear and little production, and thus didn’t match the wide, beefy bombast of the rest of the album.  There was also an extra bit of noise at the end that needed some deft editing to remove.
Careful application of EQ was applied to surgically bring out the vocals and get a little separation from the piano. From there, some M/S processing on separate EQ bands was used to move the piano more out to the sides and center the vocals.
Editing out the etxra bits at the end was difficult – a simple fade would’ve also cut out the actual tail of the piano and sounded unnatural, and a straight-ahead cut-edit would’ve sounded even worse. Instead, a cut edit was applied, but the final tail of the piano to the point where the noise began was timestretched very slightly and faded, to give it a more natural tail, while some “silent” room ambience sampled from the beginning of the track was crossfaded in to provide more natural-sounding ambience.