The term harmony has connotations more than one. Social Harmony should refer to 'peaceful coexistence' of people from different and distinct nationalities/races/religions/creeds/cas… in a given society . A' pluralistic society' which is more or less universal today with improved transport/communications/opportunities migration and mingling with people of other countries/areas being common the very existence and prosperity of a given society depends on social harmony.
Social change in terms of intercaste marriages ,gradual disintegration of rigidity of certain customs and so on did help to certain extent in furthering social harmony.
Tradition doesnot preach intolerance and cultural continuum in any country is based on its 'multplicity' of the general mainstream.
Modern philosophy has pluralism at its heart in theory but fissiparous tendencies gained theoritical and religious sanction through even educated espousing fundamentalism and the like. AlQaieda's head and vice chief are professionally qualified science students. The rigidity not with standing the undercurrent of unpublished/unadvertized modern thought of middle class growing in number is of 'live and let live'.
The other connotation is peculiarly from people of eminence like Iqbal who wrote 'saare jahaan se ' and then championed cause of theological Pakistan. Harmony advocated but not to be practised? Or harmony of other brand is that you be away and separate so that harmony is automatically achieved? Be it as it may social harmony is the ultimate wisdom for survival of human race.