constructFilter = function(arg){

	if ( !arg.filter ) { return null; }

	else if ( lodash__WEBPACK_IMPORTED_MODULE_3___default.a.isArray(arg.filter) ) {
		return arg.filter.map(function(filterArg){
			return {
				type : filterArg.type || 'lowpass',
				frequency : filterArg.frequency || 600,
				q : filterArg.q || 1,
				env : filterArg.env || null,
			};
		});
	}
	else {
		return [{
			type : arg.filter.type || 'lowpass',
			frequency : arg.filter.frequency || 600,
			q : arg.filter.q || 1,
			env : arg.filter.env ||null,
		}];
	}
}
Set up the default filter and filter envelope. *