The more difficult four-part pieces should be broken down into smaller parts both vertically and horizontally. To break it down horizontally into smaller parts, each voice part (soprano, alto, tenor, or bass) should be learned individually. In this INDIVIDUAL VOICE-PART method ("fifteen-step method"), maintaining independence of parts is made easier, and progressing from one step to another is not as difficult as in the seven-step method. However, there are more steps.
As in the three- and seven-step methods, each step should begin slowly, working gradually towards a designated tempo and thoroughly mastered before proceeding to the next. Thorough review of any needed step is useful.