The Mozart effect began with a short letter in Nature in 1993. Frances Rauscher, Gordon Shaw and Katherine Ky reported that college students who had just listened to about ten minutes of Mozart’s Sonata for Two Pianos in D major, K. 448, did better on spatial reasoning tasks than after silence or a relaxation recording. The advantage was short-lived, and the study said nothing about general intelligence or about babies.
Media and marketing nonetheless turned it into the promise that classical music makes children cleverer. Later research was far less impressive: a 1999 meta-analysis in Nature found any effect to be small, and a 2001 experiment showed that it disappeared once differences in arousal and mood between listening conditions were taken into account. Lively music that people enjoy can briefly lift alertness, whoever wrote it.
The same caution applies to lo-fi. Pleasant music can make work feel easier, which is worth something, but it is not a brain booster.