Musicians often use mental practice for enhancing performance, but individuals may have different preferences and skills in their characteristic, individually successful ways of carrying out such practice. In this study, we focus on the approaches to mental practice of four pianists who, according to the ratings of a panel of expert judges, showed outstanding improvement in their performances following their mental practice of a new piece in at least one of the two conditions: silent reading of the score or reading the score while simultaneously listening to the music. The four pianists’ approaches to mental practice were studied through self-reports in post-task interviews that were compared with eye-tracking data gathered during the actual mental practice. In successful mental practice, the pianists relied on their experience and the skills they had practised in audiation, use of recordings, imaginary rehearsal, and structural analysis. The results encourage musicians to explore their characteristic approaches to mental practice, and to deliberately practise and develop versatile mental practice skills in order to apply them flexibly in different musical situations. Eye tracking was found to be a useful tool for validating and supplementing musicians’ subjective self-descriptions and for revealing covert mental processes in the context of music reading.