The legato technique allows for you to play certain notes, without even having to play them with your right hand or playing hand. The playing hand initially plays one or various strings and it is then up to the marking hand on the fretboard to make use of the residual sound of the string to play different notes. It is this techniques which is used by musicians to play different notes at a high pace. Very few people will actually play each note individually with both their marking and playing hand at a high tempo. This technique is ideal for playing notes in a scale at a high pace and does take some practice to execute properly.
Make sure that when you are making use of this technique, that you hit the strings hard enough with your marking hand on the fretboard. By playing them too softly, it will be difficult to get the same sound result at a volume which can be properly interpreted.