You need to come up with ways to involve all of the students. Competition is usually a great way to make the participation happen. Games and competition get students involved. The results of this competition need to be visible somewhere in the school setting. Students need to feel proud of their accomplishments.
Accountability needs to be an ingredient.
Students need to realize that they have responsibility for the activities with the computer. This can come about through assignments done at regularly scheduled time with the music classroom computer or accessible computers elsewhere. If your school has a media center, computers might be available there for student use on music assignments. If a computer lab is available at your music time or at other times during the day, this could be an answer. Every school has different facilities.