diff --git a/src/types.rs b/src/types.rs
index 05a30b0..9abb612 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -32,6 +32,11 @@ impl MetadataType {
     }
 }
 
+#[derive(Debug)]
+pub enum Properties {
+    Duration,
+}
+
 pub fn all_metadata_types() -> Vec<Type> {
     vec![
         Type::Album,