Index: trunk/lib/Ripper.pm
===================================================================
--- trunk/lib/Ripper.pm	(revision 26)
+++ trunk/lib/Ripper.pm	(revision 28)
@@ -42,5 +42,5 @@
 
     # MusicBrainz discid metadata
-    my $discid = $self->tracks->get_musicbrainz_discid;
+    my $discid = $self->tracks->discid;
 
     # copy to permanent location
Index: trunk/lib/Tracks.pm
===================================================================
--- trunk/lib/Tracks.pm	(revision 26)
+++ trunk/lib/Tracks.pm	(revision 28)
@@ -22,4 +22,11 @@
     is      => 'rw',
     default => sub { [] },
+);
+
+has discid => (
+    is       => 'ro',
+    builder  => '_calculate_musicbrainz_discid',
+    lazy     => 1,
+    init_arg => undef,
 );
 
@@ -131,5 +138,5 @@
 
 # https://musicbrainz.org/doc/Disc_ID_Calculation
-sub get_musicbrainz_discid {
+sub _calculate_musicbrainz_discid {
     my ($self) = @_;