McDonald's trademark is not a copyright, so that's a different process. The trademark is appraisable too, but it's trickier because trademark doesn't expire and the stream of payments may not end. You can look at the history of franchise payments as one measure, and consumer revenues as another measure, but you'll need to discount for the actual product. The corporation broadly accounts for the value of the trademark and other things in Goodwill on the balance sheet.

For a copyrighted work, you would examine the work, find similar works, what were the stream of payments for similar works. Take into account age of the work, the artist's other works, etc.

McDonald's does hold copyright in many things. But many of those are unlikely to produce significant income; training videos, promotional materials, etc don't tend to sell for much if at all.

If you needed to appraise a new song by a popular artist, you could do a reasonable job by looking at the stream of payments generated by their average song, and projecting future payments based on the general trends of payments for songs over time. You might also consider current popularity of the artist/song and how that impacts longevity; songs don't acheive many sales initially often hit zero sales and never come back, whereas songs that chart tend to have continued, if meager, sales for a long time.