Mental practice (MP) in music refers to the ability to rehearse music in the mind without any muscular movements or acoustic feedback. While previous studies have shown the effects of the combination of MP and physical practice (PP) on instrumental performance, here we aimed to assess MP and PP effects on memory abilities. During a 1-week music practice protocol, classical guitarists were asked to practice a new musical piece using either a combination of MP and PP or PP alone. We asked participants to perform the piece and notate it at 3 different times: Day 1 and Day 7 of the 1-week practice protocol and 10 days after its completion (follow-up session). Results showed that the combination of MP and PP improves both notation and performance tasks compared with PP alone. Furthermore, we observed a clearer difference in memory performance in the follow-up session as compared with that on Day 7. Our results show that musicians can use both MP and PP to improve long-term retention and reduce physical workload and playing-related overuse injuries. Therefore, we encourage music educators to teach MP in the classrooms rather than letting students discover it in a serendipitous way.