diff --git a/src/library/beets.rs b/src/library/beets.rs
index e9c1f2e..b042e6f 100644
--- a/src/library/beets.rs
+++ b/src/library/beets.rs
@@ -16,6 +16,33 @@ use crate::{Album, AlbumId, Artist, ArtistId, Track, TrackFormat};
 
 use super::{Error, Library, Query, QueryOption};
 
+macro_rules! list_format_separator {
+    () => {
+        " -*^- "
+    };
+}
+
+const CMD_LIST: &str = "ls";
+const LIST_FORMAT_SEPARATOR: &str = list_format_separator!();
+const LIST_FORMAT_ARG: &str = concat!(
+    "--format=",
+    "$albumartist",
+    list_format_separator!(),
+    "$year",
+    list_format_separator!(),
+    "$album",
+    list_format_separator!(),
+    "$track",
+    list_format_separator!(),
+    "$title",
+    list_format_separator!(),
+    "$artist",
+    list_format_separator!(),
+    "$format"
+);
+const TRACK_FORMAT_FLAC: &str = "FLAC";
+const TRACK_FORMAT_MP3: &str = "MP3";
+
 trait QueryOptionArgBeets {
     fn to_arg(&self, option_name: &str) -> Option<String>;
 }
@@ -94,29 +121,23 @@ pub trait BeetsLibraryExecutor {
 }
 
 /// Beets library.
-pub struct BeetsLibrary {
-    executor: Box<dyn BeetsLibraryExecutor + Send + Sync>,
+pub struct BeetsLibrary<BLE> {
+    executor: BLE,
 }
 
 trait LibraryPrivate {
-    const CMD_LIST: &'static str;
-    const LIST_FORMAT_SEPARATOR: &'static str;
-    const LIST_FORMAT_ARG: &'static str;
-    const TRACK_FORMAT_FLAC: &'static str;
-    const TRACK_FORMAT_MP3: &'static str;
-
     fn list_cmd_and_args(query: &Query) -> Vec<String>;
     fn list_to_artists(list_output: Vec<String>) -> Result<Vec<Artist>, Error>;
 }
 
-impl BeetsLibrary {
+impl<BLE: BeetsLibraryExecutor> BeetsLibrary<BLE> {
     /// Create a new beets library with the provided executor, e.g. [`BeetsLibraryCommandExecutor`].
-    pub fn new(executor: Box<dyn BeetsLibraryExecutor + Send + Sync>) -> BeetsLibrary {
+    pub fn new(executor: BLE) -> Self {
         BeetsLibrary { executor }
     }
 }
 
-impl Library for BeetsLibrary {
+impl<BLE: BeetsLibraryExecutor> Library for BeetsLibrary<BLE> {
     fn list(&mut self, query: &Query) -> Result<Vec<Artist>, Error> {
         let cmd = Self::list_cmd_and_args(query);
         let output = self.executor.exec(&cmd)?;
@@ -124,37 +145,10 @@ impl Library for BeetsLibrary {
     }
 }
 
-macro_rules! list_format_separator {
-    () => {
-        " -*^- "
-    };
-}
-
-impl LibraryPrivate for BeetsLibrary {
-    const CMD_LIST: &'static str = "ls";
-    const LIST_FORMAT_SEPARATOR: &'static str = list_format_separator!();
-    const LIST_FORMAT_ARG: &'static str = concat!(
-        "--format=",
-        "$albumartist",
-        list_format_separator!(),
-        "$year",
-        list_format_separator!(),
-        "$album",
-        list_format_separator!(),
-        "$track",
-        list_format_separator!(),
-        "$title",
-        list_format_separator!(),
-        "$artist",
-        list_format_separator!(),
-        "$format"
-    );
-    const TRACK_FORMAT_FLAC: &'static str = "FLAC";
-    const TRACK_FORMAT_MP3: &'static str = "MP3";
-
+impl<BLE: BeetsLibraryExecutor> LibraryPrivate for BeetsLibrary<BLE> {
     fn list_cmd_and_args(query: &Query) -> Vec<String> {
-        let mut cmd: Vec<String> = vec![String::from(Self::CMD_LIST)];
-        cmd.push(Self::LIST_FORMAT_ARG.to_string());
+        let mut cmd: Vec<String> = vec![String::from(CMD_LIST)];
+        cmd.push(LIST_FORMAT_ARG.to_string());
         cmd.append(&mut query.to_args());
         cmd
     }
@@ -168,7 +162,7 @@ impl LibraryPrivate for BeetsLibrary {
                 continue;
             }
 
-            let split: Vec<&str> = line.split(Self::LIST_FORMAT_SEPARATOR).collect();
+            let split: Vec<&str> = line.split(LIST_FORMAT_SEPARATOR).collect();
             if split.len() != 7 {
                 return Err(Error::InvalidData(line.to_string()));
             }
@@ -193,8 +187,8 @@ impl LibraryPrivate for BeetsLibrary {
                 title: track_title,
                 artist: track_artist.split("; ").map(|s| s.to_owned()).collect(),
                 format: match track_format.as_ref() {
-                    Self::TRACK_FORMAT_FLAC => TrackFormat::Flac,
-                    Self::TRACK_FORMAT_MP3 => TrackFormat::Mp3,
+                    TRACK_FORMAT_FLAC => TrackFormat::Flac,
+                    TRACK_FORMAT_MP3 => TrackFormat::Mp3,
                     _ => return Err(Error::InvalidData(track_format)),
                 },
             };
@@ -309,14 +303,14 @@ mod tests {
                 let track_title = &track.title;
                 let track_artist = &track.artist.join("; ");
                 let track_format = match track.format {
-                    TrackFormat::Flac => BeetsLibrary::TRACK_FORMAT_FLAC,
-                    TrackFormat::Mp3 => BeetsLibrary::TRACK_FORMAT_MP3,
+                    TrackFormat::Flac => TRACK_FORMAT_FLAC,
+                    TrackFormat::Mp3 => TRACK_FORMAT_MP3,
                 };
 
                 strings.push(format!(
                     "{album_artist}{0}{album_year}{0}{album_title}{0}\
                      {track_number}{0}{track_title}{0}{track_artist}{0}{track_format}",
-                    BeetsLibrary::LIST_FORMAT_SEPARATOR,
+                    LIST_FORMAT_SEPARATOR,
                 ));
             }
         }
@@ -356,7 +350,7 @@ mod tests {
 
     #[test]
     fn test_list_empty() {
-        let arguments = vec!["ls".to_string(), BeetsLibrary::LIST_FORMAT_ARG.to_string()];
+        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
         let result = Ok(vec![]);
 
         let mut executor = MockBeetsLibraryExecutor::new();
@@ -366,7 +360,7 @@ mod tests {
             .times(1)
             .return_once(|_| result);
 
-        let mut beets = BeetsLibrary::new(Box::new(executor));
+        let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&Query::default()).unwrap();
 
         let expected: Vec<Artist> = vec![];
@@ -375,7 +369,7 @@ mod tests {
 
     #[test]
     fn test_list_ordered() {
-        let arguments = vec!["ls".to_string(), BeetsLibrary::LIST_FORMAT_ARG.to_string()];
+        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
         let expected = COLLECTION.to_owned();
         let result = Ok(artists_to_beets_string(&expected));
 
@@ -386,7 +380,7 @@ mod tests {
             .times(1)
             .return_once(|_| result);
 
-        let mut beets = BeetsLibrary::new(Box::new(executor));
+        let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&Query::default()).unwrap();
 
         assert_eq!(output, expected);
@@ -394,7 +388,7 @@ mod tests {
 
     #[test]
     fn test_list_unordered() {
-        let arguments = vec!["ls".to_string(), BeetsLibrary::LIST_FORMAT_ARG.to_string()];
+        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
         let mut expected = COLLECTION.to_owned();
         let mut output = artists_to_beets_string(&expected);
         let last = output.len() - 1;
@@ -421,7 +415,7 @@ mod tests {
             .times(1)
             .return_once(|_| result);
 
-        let mut beets = BeetsLibrary::new(Box::new(executor));
+        let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&Query::default()).unwrap();
 
         assert_eq!(output, expected);
@@ -429,7 +423,7 @@ mod tests {
 
     #[test]
     fn test_list_album_title_year_clash() {
-        let arguments = vec!["ls".to_string(), BeetsLibrary::LIST_FORMAT_ARG.to_string()];
+        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
         let mut expected = COLLECTION.to_owned();
         expected[0].albums[0].id.year = expected[1].albums[0].id.year;
         expected[0].albums[0].id.title = expected[1].albums[0].id.title.clone();
@@ -443,7 +437,7 @@ mod tests {
             .times(1)
             .return_once(|_| result);
 
-        let mut beets = BeetsLibrary::new(Box::new(executor));
+        let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&Query::default()).unwrap();
 
         assert_eq!(output, expected);
@@ -458,7 +452,7 @@ mod tests {
 
         let arguments = vec![
             "ls".to_string(),
-            BeetsLibrary::LIST_FORMAT_ARG.to_string(),
+            LIST_FORMAT_ARG.to_string(),
             String::from("^album:some.album"),
             String::from("track:5"),
             String::from("artist:some.artist"),
@@ -472,7 +466,7 @@ mod tests {
             .times(1)
             .return_once(|_| result);
 
-        let mut beets = BeetsLibrary::new(Box::new(executor));
+        let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&query).unwrap();
 
         let expected: Vec<Artist> = vec![];
diff --git a/src/main.rs b/src/main.rs
index 04ab395..81a8fab 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -41,9 +41,9 @@ fn main() {
     // Create the application.
     let opt = Opt::from_args();
 
-    let beets = BeetsLibrary::new(Box::new(
+    let beets = BeetsLibrary::new(
         BeetsLibraryCommandExecutor::default().config(opt.beets_config_file_path.as_deref()),
-    ));
+    );
 
     let database = JsonDatabase::new(Box::new(JsonDatabaseFileBackend::new(
         &opt.database_file_path,
diff --git a/tests/library/beets.rs b/tests/library/beets.rs
index efdecbf..bea16d0 100644
--- a/tests/library/beets.rs
+++ b/tests/library/beets.rs
@@ -15,19 +15,21 @@ use musichoard::{
 
 use crate::COLLECTION;
 
-static BEETS_EMPTY_CONFIG: Lazy<Arc<Mutex<BeetsLibrary>>> = Lazy::new(|| {
-    Arc::new(Mutex::new(BeetsLibrary::new(Box::new(
-        BeetsLibraryCommandExecutor::default(),
-    ))))
-});
+static BEETS_EMPTY_CONFIG: Lazy<Arc<Mutex<BeetsLibrary<BeetsLibraryCommandExecutor>>>> =
+    Lazy::new(|| {
+        Arc::new(Mutex::new(BeetsLibrary::new(
+            BeetsLibraryCommandExecutor::default(),
+        )))
+    });
 
-static BEETS_TEST_CONFIG: Lazy<Arc<Mutex<BeetsLibrary>>> = Lazy::new(|| {
-    Arc::new(Mutex::new(BeetsLibrary::new(Box::new(
-        BeetsLibraryCommandExecutor::default().config(Some(
-            &fs::canonicalize("./tests/files/library/config.yml").unwrap(),
-        )),
-    ))))
-});
+static BEETS_TEST_CONFIG: Lazy<Arc<Mutex<BeetsLibrary<BeetsLibraryCommandExecutor>>>> =
+    Lazy::new(|| {
+        Arc::new(Mutex::new(BeetsLibrary::new(
+            BeetsLibraryCommandExecutor::default().config(Some(
+                &fs::canonicalize("./tests/files/library/config.yml").unwrap(),
+            )),
+        )))
+    });
 
 #[test]
 fn test_no_config_list() {