A conductor’s most valuable tools are his or her ear and hand. They need a good inner ear to be able to create a sound-image of a piece they are conducting and they need well developed performance error-detection skills to guide the performance towards where they want it to be. Both of those skills are expected to be developed during their formal education. However, due to the nature of the task and a limited number of hands-on practice hours, most conductors only develop the latter once they start their professional career. Considering the major role that computers have in modernizing education, it is only a matter of time when computer-assisted instruction will become a part of every music student’s education. Many ear training tools have been developed and are informally used by numerous music teachers. However, most of these applications use MIDI files and focus on standard ear training such as identifying intervals and chords, melodic or rhythmic dictation etc. There is a clear gap fit for a performance error-detection tool with realistic audio examples. This thesis offers an overview of possibilities for e-learning in music education and reviews scientific literature regarding computer-assisted music instruction. Additionally, motivational elements of instructional design and game theory, within the context of music education, are explored. In addition to the review of literature, the design and implementation process of a user interface for ChoirCube is described. ChoirCube is an ongoing project that aims to provide a realistic web-based ear training tool for choir conductors based on professional quality studio recordings of a choir. The web application is partially developed using current web technologies (HTML5 and JavaScript). Since this stage of development focused on design of the user interface various score display and annotation methods are presented and discussed. Finally, a summarized overview of technology in music education is offered. Aditionally the current state of ChoirCube project is described together with propositions for future improvements.