Current musical composition software on the commercial market is well-functioned for most users. However, there remains no program suitable for people with severe disabilities. In this paper a musical composition assistant is designed for individuals that require assistance using a musical composition tool, with special consideration for the people with physical and visual disabilities. In the single-switch mode a musical composition assistant first initiates a cursor, which moves across the top of each row (referred to as row scanning) for pitch, beat, octave, and halftone selection. To select a note option, the users have to press the mini switch connected to the left key when the cursor is over the row containing the desired entry. In the double-switch mode, the users can control two mini switches connected to the left and right key, with the right key to select and the left key to verify. The additional tools; scanning keyboard and scanning mouse were provided for some users with severe disabilities to write lyrics and share their composition ideas with others. After a 90-day experiment, 10 participants carried out the composition learning task with 110 notes/hr composing speed.