Original: While some composers , notably Mozart , have used this interval to advantage in melodic composition , other composers , having felt it to be an awkward leap , particularly in vocal music , considered a whole step between these two scale degrees more conducive to smooth melody writing , so either the subtonic seventh was used or the sixth scale degree raised .
Simplified: They thought that a whole step between these two scale degrees was better for smooth melody writing , so they used the subtonic seventh , or raised the sixth scale degree .