This doctoral thesis presents an analysis of the multitasking processes involved in musical accompaniment and simultaneous interpretation. The analysis incorporates the study of theoretical models and adopts as a framework three comparative scenarios: sight-reading versus sight translation, sight-read musical accompaniment versus simultaneous interpretation with text and improvised musical accompaniment versus simultaneous interpretation without text. In addition, the description of the teaching methods used at four music training institutions provides details of the training regimens that enable students to acquire the required skills of sight-reading, musical accompaniment and improvisation. The empirical part includes a quantitative comparison of the multitasking ability of students who have undergone different types of musical and language training. The results show that students with musical background outperform those without such background on a multitasking test, while students with better knowledge of their first foreign language outperformed those without such knowledge on a simultaneous interpretation test.