musescore/MuseScore — pull request #996 by shredpub (2014-06-21 16:18:24+00:00)
Title: Swing Playback functionality with user controlled swing ratio implemented

From Style->General, user can select among eighth note swing, sixteenth note swing, and set the swing ratio in percentage. (60 => 60/40 swing)
Doing this will enable the score to swing according to the set parameters.