An experiment in Brazil compared the effects of exposing breast cancer cells in culture to Beethoven's Fifth Symphony, Mozart's Sonata for Two Pianos in D, and Ligeti's "Atmosphères." The experiment indeed concluded that Beethoven's Fifth and "Atmosphères" had facilitated cell death in laboratory conditions, as compared to Mozart's Sonata or complete silence.

However, this experiment was not carried out on mice or humans, only on cancer cells isolated in petri dishes. The Brazilian team did not identify which aspect or aspects of the musical pieces had resulted in cell death, and there is no way to know how healthy tissue would react. Also, the researcher said the methods her team used did not allow it to quantify cell death, informing Snopes that the 20% figure was made up.

The most outlandish aspects of this claim ranged from exaggerated to false. The earliest version Snopes could find appeared in a report published in 2011 in a Brazilian newspaper. The report was later picked up by U.S. news outlets.

The lead scientist said she did an interview with CNN Radio in Brazil to clarify her team's findings. Snopes could not find the interview. Later, she stopped investigating the effects of music on cells because she said she lacked funding.