A Nature article suggests it's music training in general with regard to verbal memory: "...adults who received music training before the age of 12 have a better memory for spoken words than those who did not. Music training in childhood may therefore have long-term positive effects on verbal memory." http://www.nature.com/nature/journal/v396/n6707/abs/396128a0... I do wonder if the same effect would result with any memory-intensive task. Reading and playing music would have to be one of the most intensive and enjoyable, however.