geon ing ▁Russian ▁compos ers ▁as ▁well ▁as ▁each ▁composer ' s ▁endeav ours . ▁ ▁Bour g ault ▁was ▁also ▁interested ▁in ▁historical ▁figures , ▁not ably ▁fellow ▁Bret ons , ▁and ▁in ▁collect ing ▁and ▁editing ▁Bre ton ▁folk ▁music , ▁of ▁which ▁he ▁was ▁a ▁pione er . ▁He ▁wrote ▁oper as ▁dealing ▁with ▁both ▁Vas co ▁da ▁G ama ▁and ▁Anne ▁of ▁Brit t any . ▁He ▁wrote ▁many ▁other ▁oper as , ▁ch oral ▁works ▁and ▁orch est ral ▁music ▁and ▁published ▁several ▁collections ▁of ▁fol ks ongs , ▁mainly ▁Greek , ▁Bre ton , ▁Irish , ▁Wel sh , ▁and ▁Scottish . ▁Among ▁his ▁final ▁compos itions ▁was ▁a ▁mass . ▁He ▁also ▁wrote ▁a ▁bi ography ▁of ▁Franz ▁Sch ub ert . ▁Bour g ault ' s ▁primary ▁libre tt ist ▁was ▁Louis ▁Gal let . ▁ ▁He ▁gave ▁a ▁lecture ▁concerning ▁his ▁philosophy ▁at ▁the ▁ 1 8 7 8 ▁Universal ▁Ex hib ition ▁in ▁Paris . ▁He ▁said : ▁ ▁No ▁element ▁of ▁expression ▁existing ▁in ▁a ▁t une ▁of ▁any ▁kind , ▁however ▁ancient , ▁however ▁remote ▁in ▁origin , ▁must ▁be ▁ban ished ▁from ▁our ▁musical ▁id iom . ▁All ▁modes , ▁old ▁and ▁new , ▁European ▁or ▁ex otic , ▁in so far ▁as ▁they ▁are ▁capable ▁of ▁serving ▁an ▁express ive ▁purpose , ▁must ▁be ▁admitted ▁by ▁us ▁and ▁used ▁by ▁compos ers . ▁I ▁believe ▁that ▁the ▁poly ph onic ▁principle ▁may ▁be ▁applied ▁to ▁all ▁kinds ▁of ▁scales