Observablecollection not updating list, when an item gets added

I'm using the MVVM pattern and want to update a ListView using an observable collection. I went through several SO questions, but cannot see what I'm doing wrong. Any help is much appreciated. Thanks.

View.xaml

Namespace: xmlns:local="clr-namespace:MusicPlayer.ViewModel"

DataContext

<UserControl.DataContext>
    <local:AllTracksViewModel/>
</UserControl.DataContext>

ListView

<ListView x:Name="TrackListView" 
                  ItemsSource="{Binding Path=TrackListObservable}">
...
<ListView.View>
   <GridView>
     <GridViewColumn Header="Title" Width="250" DisplayMemberBinding="{Binding Title}" />
      <GridViewColumn Header="Album" Width="200" DisplayMemberBinding="{Binding Album}" />
      <GridViewColumn Header="Artist" Width="150" DisplayMemberBinding="{Binding Artist}" />
      <GridViewColumn Header="Duration" Width="100" DisplayMemberBinding="{Binding FormattedDuration}" />
      </GridView>
    </ListView.View>
</ListView>

ViewModel.cs

public class AllTracksViewModel
{
    public ObservableCollection<Track> TrackListObservable { get; private set; }

    public AllTracksViewModel()
    {
        TrackListObservable = new ObservableCollection<Track>();
    }
}

I verified that items are definitely getting added to the observable. Again, thanks for the help.