This pilot study focuses on the use of mobile tablets to allow secondary students to compose in class with the application "GarageBand." The empirical research has two aims: to demonstrate the possibility of using mobile tablets as a composing device, and to examine professional practices for using mobile technologies in music learning. A 12-week e-learning curriculum was specially designed for students to learn to use mobile tablets to compose popular music. A total of 159 secondary school students participated in the study and responded to a set of pre- and post-activity questionnaires, modelled on items developed for a motivational study by McPherson and O'Neill (2010). The paired sample t-test compared the mean score changes in the dimensions of intrinsic value, attainment value, utility value, perceived cost and expectancy in motivation. Furthermore, one-way analysis of variance compared the mean scores for scale questions on learning motivation between groups based on number of years spent learning to play an instrument as revealed by the student survey. The findings of SPSS analysis reveal that both non-instrument learners and instrument learners showed significant increases in motivation when using mobile tablets as an instrument to compose popular music in class. Different modes of learning, limitations and suggestions are also discussed in mobile composing.