The Bowie Bonds (2013)

"In 2004, the rating agency Moody’s Investors Service downgraded the Bowie bonds (to Baa1, a step above “junk” status)...Yet this downgrade only would’ve been a problem had Prudential wanted to sell its bonds, as they were now considered to be of lesser credit quality. As far as we know, Prudential didn’t. Instead, the Bowie bonds sat in Prudential’s coffers, generating who knows how much in terms of royalty payments for a decade. It’s likely his royalties decreased in the early 2000s, but Bowie was never in any remote danger of losing his songs."

The price of a bond is merely the value of its future cash flows... If the price fell as Moody's thought (to just above junk!), that implies the expected cash flows (royalties) did too, because the royalties determine the price. It is irrelevant to the question of profit whether Prudential sold them or not - selling/holding was merely a question of whether they wanted to take their losses up front (by selling them at the now lower market value) or over time (by receiving lower royalties than they had predicted when they negotiated to buy the bonds).

And we can guess pretty safely that the Bowie bonds did not do well. They were sold at the height of a bubble before the Internet impact on sales became apparent, no one wanted to do such deals after a few imitators did, the decay in bond quality was so obvious a ratings agency would downgrade them, Prudential doesn't appear to want to discuss them given the paucity of available details in this and other writeups I've seen (despite the glamor of the association & being one of the very few financial instruments the public is interested in), and Bowie's career during the described bond period wouldn't've helped the royalties outperform the general music market either (some anniversary albums, plus a lot of live touring whose income presumably didn't go to the bonds - and perhaps that was precisely why he did so many, a kind of moral hazard).