diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 957527a..251a87e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -66,7 +66,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install ruff pytest
+          pip install -e ".[dev]"
 
       - name: Run tests with pytest
         run: pytest
diff --git a/src/sse/base.py b/src/sse/base.py
new file mode 100644
index 0000000..bd1ce1e
--- /dev/null
+++ b/src/sse/base.py
@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+
+import abc
+
+import numpy as np
+
+
+class SoundSourceLocatorBase(abc.ABC):
+    @abc.abstractmethod
+    def fit_transform(
+        self,
+        X: np.ndarray,
+    ) -> np.ndarray:
+        pass
diff --git a/src/sse/music_v2.py b/src/sse/music_v2.py
new file mode 100644
index 0000000..b049c7f
--- /dev/null
+++ b/src/sse/music_v2.py
@@ -0,0 +1,96 @@
+# -*- coding: utf-8 -*-
+
+import numpy as np
+
+from sse.base import SoundSourceLocatorBase
+
+
+class MusicSoundSourceLocator(SoundSourceLocatorBase):
+    """Music Sound Source Locator."""
+
+    def __init__(
+        self,
+        fs: float,
+        d: float,
+        c: float = 340.0,
+        N_theta: int = 180,
+    ):
+        """Implementation of MUSIC method.
+
+        Args:
+            fs: Sampling frequency [Hz].
+            d: distance between mics.
+            c: sound speed. Defaults to 340.0.
+            N_theta (int, optional): _description_. Defaults to 180.
+        """
+
+        self.fs = fs  # sampling frequency [Hz].
+        self.T = 1.0 / fs  # sampling Term [sec].
+        self.d = d  # mic. distance [m].
+        self.k = None  # data index series [point].
+        self.L = None  # data length [point].
+        self.c = c  # sound speed [m/sec].
+        self.N_theta = N_theta
+        self.N_ch = None
+
+        self.minvec = None
+        self.thetas = None
+
+    def fit_transform(
+        self,
+        X: np.ndarray,
+        y: np.ndarray | None = None,
+    ) -> "MusicSoundSourceLocator":
+        # x: input sound signal
+        # x.shape = (sample, N_ch)
+
+        self.L = len(X) // 1
+        self.k = np.arange(self.L // 2)
+        self.N_ch = X.shape[1]
+
+        winfunc = np.hanning(len(X)).reshape(-1, 1)
+
+        X_freq = np.fft.fft(winfunc * X, axis=0)[: self.L // 2, :]
+        self.R = (
+            X_freq.conj().reshape(-1, self.N_ch, 1) @ X_freq.reshape(-1, 1, self.N_ch)
+        ) / (X_freq.shape[0] / self.fs)
+
+        self.eigval, self.eigvec = np.linalg.eig(self.R)
+        self.minvec = self.eigvec[:, :, -1].reshape(-1, self.N_ch, 1)
+
+        self.thetas = np.linspace(-np.pi / 2, np.pi / 2, self.N_theta)
+        self.S = self._calc_s_music(self.thetas)
+        return self._theta_hat()
+
+    def _theta_hat(self):
+        return np.rad2deg(self.thetas[(np.abs(self.S) ** 2).mean(0).argmax()])
+
+    def _calc_s_music(self, thetas):
+        return np.array(
+            [
+                np.sum(self._calc_alpha(theta).conj() * self._calc_alpha(theta), axis=0)
+                / np.abs(
+                    self.minvec.conj().transpose(0, 2, 1)
+                    @ self._calc_alpha(theta).transpose(1, 0).reshape(-1, self.N_ch, 1)
+                ).squeeze()
+                ** 2
+                for theta in thetas
+            ]
+        ).T * np.sqrt(
+            self.eigval[:, 0][:, None]
+        )  # / (self.eigval[:, -1][:, None]+1e-8) )
+
+    def _calc_alpha(self, theta):
+        return np.array(
+            [
+                np.ones(len(self.k)),
+                np.exp(
+                    2j
+                    * np.pi
+                    * self.d
+                    * np.sin(theta)
+                    / (self.c * self.T)
+                    * ((self.k) / (len(self.k) * 2))
+                ),
+            ]
+        )
diff --git a/tests/test_music.py b/tests/test_music.py
new file mode 100644
index 0000000..de5bab8
--- /dev/null
+++ b/tests/test_music.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+
+import numpy as np
+
+from sse.music_v2 import MusicSoundSourceLocator
+
+
+class TestMusicSoundSourceLocator:
+    def test_fit_transform(self):
+        self.locator = MusicSoundSourceLocator(
+            fs=16000,
+            d=1.0,
+        )
+        X = np.random.randn(1000, 2)
+        out = self.locator.fit_transform(X=X)
+        print(out)