diff --git a/Cargo.toml b/Cargo.toml
index e650491..d56eeb8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,7 +17,7 @@ thiserror = "2.0.18"
 tokio = { version = "1.51.0", features = ["full"] }
 tracing = "0.1.44"
 tracing-subscriber = { version = "0.3.23", features = ["env-filter"] }
-uuid = { version = "1.23.0", features = ["v4"] }
+uuid = { version = "1.23.0", features = ["v4", "serde"] }
 rand = "0.10.0"
 sqlx = { version = "0.8.6", features = ["runtime-tokio-rustls"] }
 async-trait = "0.1.89"
diff --git a/crates/domain/src/lib.rs b/crates/domain/src/lib.rs
index 59755c1..f0ee140 100644
--- a/crates/domain/src/lib.rs
+++ b/crates/domain/src/lib.rs
@@ -7,5 +7,7 @@ pub mod transposer;
 pub use note::Note;
 pub use chord::Chord;
 pub use song::{ChordPosition, LyricLine, Section, SectionKind, SongMeta, Song};
+pub use song::{song_preview_chords, StoredSong, SongSummary};
 pub use ports::{FetchError, ParseError, TabFetcherPort, TabParserPort, TabSource};
+pub use ports::{RepositoryError, SongRepositoryPort};
 pub use transposer::{ChordTransposer, TransposeError};
diff --git a/crates/domain/src/ports.rs b/crates/domain/src/ports.rs
index fc70f25..7a358c2 100644
--- a/crates/domain/src/ports.rs
+++ b/crates/domain/src/ports.rs
@@ -35,3 +35,22 @@ pub trait TabFetcherPort: Send + Sync {
 pub trait TabParserPort: Send + Sync {
     fn parse(&self, html: &str) -> Result<Song, ParseError>;
 }
+
+use uuid::Uuid;
+use crate::song::{StoredSong, SongSummary};
+
+#[derive(Debug, Error)]
+pub enum RepositoryError {
+    #[error("Song not found")]
+    NotFound,
+    #[error("Database error: {0}")]
+    Internal(String),
+}
+
+#[async_trait]
+pub trait SongRepositoryPort: Send + Sync {
+    async fn save(&self, song: &Song) -> Result<StoredSong, RepositoryError>;
+    async fn list(&self) -> Result<Vec<SongSummary>, RepositoryError>;
+    async fn get(&self, id: Uuid) -> Result<Option<Song>, RepositoryError>;
+    async fn delete(&self, id: Uuid) -> Result<(), RepositoryError>;
+}
diff --git a/crates/domain/src/song.rs b/crates/domain/src/song.rs
index e3f26f6..7eaaba4 100644
--- a/crates/domain/src/song.rs
+++ b/crates/domain/src/song.rs
@@ -60,6 +60,40 @@ pub struct Song {
     pub sections: Vec<Section>,
 }
 
+use uuid::Uuid;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct StoredSong {
+    pub id: Uuid,
+    pub song: Song,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SongSummary {
+    pub id: Uuid,
+    pub meta: SongMeta,
+    pub preview_chords: Vec<String>,
+}
+
+pub fn song_preview_chords(song: &Song) -> Vec<String> {
+    let mut seen = std::collections::HashSet::new();
+    let mut result = Vec::new();
+    'outer: for section in &song.sections {
+        for line in &section.lines {
+            for cp in &line.chords {
+                let name = cp.chord.name(true);
+                if seen.insert(name.clone()) {
+                    result.push(name);
+                    if result.len() >= 5 {
+                        break 'outer;
+                    }
+                }
+            }
+        }
+    }
+    result
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;