Multiple set training will produce at least some measure of muscle gains.  However, those results are stimulated by only one or two sets from each workout.  The additional sets are literally a waste of time.  In fact, because they tap into your recovery ability, the extra sets actually reduce your gains. You will gain muscle mass faster, if you keep your workout as short as possible.

Optimum muscle gains can always be achieved with a very small number of exercises by applying the greatest level of intensity of effort. Any additional exercises included in the training routine will actually reduce the degree of muscular gains.  If the excess is great enough they will actually result in a loss of both strength and muscle mass.

What is the absolute minimum amount of exercise that will produce the maximum degree of muscle gains?   An individual’s own uniqueness  makes answering that question difficult.  The quantity of exercise required for optimal progress reduces as an you grows stronger. This we know for sure.

To guarantee continual muscle gains, the quantity of exercises performed should be reduced over time.  As long as you are performing with intensity of effort, muscle gains will be made. And,  the amount of exercise required to continue making fast muscle gains will actually  lessen as you get bigger and stronger.