For all the sci-fi promises about blockchain transforming finance, the reality will be more mundane as thousands of ordinary instruments quietly move to digital ledgers. On Wednesday, it was money market funds.

Bank of New York Mellon Corp. and Goldman Sachs Group Inc. are collaborating to use blockchain technology to maintain an ownership record of money market funds.

The nation's oldest bank and a big Wall Street firm are wading into tokenization, joining a growing number of money managers experimenting with blockchain technology. The effort stops short of the expected eventual benefits of what's known as decentralized finance—allowing,