How do you call a custom serializer update method in Django rest framework?

I am trying to make a simple API that takes in an audio file, reverses it, and stores them both. It can accept the file, and overwriting the perform_create() method I reversed it. But now I can’t find a way to update the record with the reversed file. This is my viewset

class SoundViewSet(viewsets.ModelViewSet):
    queryset = Sound.objects.all().order_by('id')
    serializer_class = SoundSerializer

    def perform_create(self, serializer):
        sound = Sound.objects.last()
        root = settings.MEDIA_ROOT.replace('/media','')
        root = root +
        p = Path(root)
        clip = AudioSegment.from_wav(p)
        rev = clip.reverse()
        sound.reversedaudio = rev
        serializer = SoundSerializer(data=sound)

It is returning NULL values. I have to pass it through the serializer first because the audio file has to be parsed for JSON. I just can’t seem to find a simple way to call a serializer update() like the perform_create(). I tried Sound.objects.filter( but its a viewset update, file gets uploaded un-parsed and is basically then garbage. Here’s my serializer class:

class SoundSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = Sound
        fields = ('name', 'audio', 'reversedaudio')

Can someone point out what I’m missing?

P.s. I am using DRF for the first time and working under a deadline so I would prefer not having to define everything on my own and only working around the model classes if possible.

My first step with something like this would be to verify each and every step along the way. Either using the debugger or just adding print statements, I’d make sure that each variable has the value and data type that you’re expecting it to have at each point.