too late to filter categories if get categories is onload?

I'm not sure why the filter I'm using doesn't work, if it is too late to filter the categories once they have loaded or if I am just approaching this totally wrong.

Since updateAvailableMusic() runs onload, and filterAvailableCateories() gets run onclick from the html file as such :

"ng-click='filterAvailableCategories(party)'"

I am wondering if I need to be passing more information to the filter function. And as this is Angular and I don't really understand how to debug Angular (read: "follow it through with a breakpoint the way I would normal javascript", I am hoping to get another perspective on this and much thanks ahead of time.

Here is the code:

$scope.updateAvailableMusic = function () {
    return music.getMusicCategories(null, $scope.featureType).then(function (options) {
        $scope.availableCategoriesUnmapped = options;
        $scope.addDefaultCategories();
        $scope.availableCategories = _.groupBy(options, 'category');
    });
};
$scope.filterAvailableCategories = function (musictype) {

        $scope.availableCategories = $scope.availableCategories.filter(function (rr) {
            switch (musictype) {
            case 'party':
                if (rr.category !== 'Rap' && rr.category !== 'HipHop') {
                    return rr;
                }
                break;
            case 'study':
                if (rr.category !== 'Classical' && rr.category !== 'Jazz') {
                    return rr;
                }
                break;
            }
        });
};