diff --git a/crepe/__init__.py b/crepe/__init__.py
index 52eacea..a740984 100755
--- a/crepe/__init__.py
+++ b/crepe/__init__.py
@@ -1,2 +1,9 @@
 from .version import version as __version__
-from .core import get_activation, predict, process_file
+from .core import (
+    get_activation,
+    predict,
+    process_file,
+    to_viterbi_cents_impl,
+    to_viterbi_cents_legacy,
+    to_viterbi_cents_fast,
+)
diff --git a/crepe/cli.py b/crepe/cli.py
index aaa96de..59c26c6 100644
--- a/crepe/cli.py
+++ b/crepe/cli.py
@@ -9,6 +9,7 @@
 
 
 def run(filename, output=None, model_capacity='full', viterbi=False,
+        viterbi_impl='legacy',
         save_activation=False, save_plot=False, plot_voicing=False,
         no_centering=False, step_size=10, verbose=True):
     """
@@ -27,6 +28,8 @@ def run(filename, output=None, model_capacity='full', viterbi=False,
         :func:`~crepe.core.build_and_load_model`
     viterbi : bool
         Apply viterbi smoothing to the estimated pitch curve. False by default.
+    viterbi_impl : {'legacy', 'fast'}
+        Implementation used when `viterbi=True`.
     save_activation : bool
         Save the output activation matrix to an .npy file. False by default.
     save_plot: bool
@@ -77,6 +80,7 @@ def run(filename, output=None, model_capacity='full', viterbi=False,
         process_file(file, output=output,
                      model_capacity=model_capacity,
                      viterbi=viterbi,
+                     viterbi_impl=viterbi_impl,
                      center=(not no_centering),
                      save_activation=save_activation,
                      save_plot=save_plot,
@@ -134,6 +138,9 @@ def main():
     parser.add_argument('--viterbi', '-V', action='store_true',
                         help='perform Viterbi decoding to smooth the pitch '
                              'curve')
+    parser.add_argument('--viterbi-impl', default='legacy',
+                        choices=['legacy', 'fast'],
+                        help='implementation used when --viterbi is enabled')
     parser.add_argument('--save-activation', '-a', action='store_true',
                         help='save the output activation matrix to a .npy '
                              'file')
@@ -165,6 +172,7 @@ def main():
         output=args.output,
         model_capacity=args.model_capacity,
         viterbi=args.viterbi,
+        viterbi_impl=args.viterbi_impl,
         save_activation=args.save_activation,
         save_plot=args.save_plot,
         plot_voicing=args.plot_voicing,
diff --git a/crepe/core.py b/crepe/core.py
index 03ea52e..d246569 100644
--- a/crepe/core.py
+++ b/crepe/core.py
@@ -21,6 +21,8 @@
 # the model is trained on 16kHz audio
 model_srate = 16000
 
+viterbi_impls = ('legacy', 'fast')
+
 
 def build_and_load_model(model_capacity):
     """
@@ -124,6 +126,25 @@ def to_viterbi_cents(salience):
     Find the Viterbi path using a transition prior that induces pitch
     continuity.
     """
+    return to_viterbi_cents_impl(salience, impl='legacy')
+
+
+def to_viterbi_cents_impl(salience, impl='legacy'):
+    """
+    Find the Viterbi path using the requested implementation.
+    """
+    if impl == 'legacy':
+        return to_viterbi_cents_legacy(salience)
+    if impl == 'fast':
+        return to_viterbi_cents_fast(salience)
+    raise ValueError('expected viterbi_impl to be one of {}, got {}'.format(
+        viterbi_impls, impl))
+
+
+def to_viterbi_cents_legacy(salience):
+    """
+    Legacy hmmlearn-backed Viterbi smoothing path.
+    """
     from hmmlearn import hmm
 
     # uniform prior on the starting pitch
@@ -153,6 +174,86 @@ def to_viterbi_cents(salience):
                      range(len(observations))])
 
 
+def to_viterbi_cents_fast(salience):
+    """
+    Exact structured Viterbi smoothing path for CREPE's local transition graph.
+    """
+    observations = np.argmax(salience, axis=1).astype(np.int64, copy=False)
+    path = _viterbi_path_fast(observations)
+    return np.array([to_local_average_cents(salience[i, :], path[i]) for i in
+                     range(len(observations))])
+
+
+def _viterbi_fast_structure():
+    """
+    Precompute the exact local predecessor structure for CREPE's transition.
+    """
+    cached = getattr(_viterbi_fast_structure, 'cached', None)
+    if cached is not None:
+        return cached
+
+    states = 360
+    starting = np.ones(states, dtype=np.float64) / states
+
+    xx, yy = np.meshgrid(range(states), range(states))
+    transition = np.maximum(12 - abs(xx - yy), 0).astype(np.float64)
+    transition = transition / np.sum(transition, axis=1)[:, None]
+
+    self_emission = 0.1
+    emission = (np.eye(states, dtype=np.float64) * self_emission +
+                np.ones(shape=(states, states), dtype=np.float64) *
+                ((1 - self_emission) / states))
+
+    valid = transition > 0
+    width = int(np.max(np.sum(valid, axis=0)))
+    source_idx = np.zeros((states, width), dtype=np.int16)
+    log_trans = np.full((states, width), -np.inf, dtype=np.float64)
+
+    for target in range(states):
+        sources = np.flatnonzero(valid[:, target]).astype(np.int16)
+        source_idx[target, :len(sources)] = sources
+        log_trans[target, :len(sources)] = np.log(
+            transition[sources.astype(np.int64), target])
+
+    cached = {
+        'state_idx': np.arange(states, dtype=np.int64),
+        'log_starting': np.log(starting),
+        'source_idx': source_idx,
+        'log_trans': log_trans,
+        'log_emission': np.log(emission)
+    }
+    _viterbi_fast_structure.cached = cached
+    return cached
+
+
+def _viterbi_path_fast(observations):
+    """
+    Exact structured Viterbi decode of CREPE's argmax observations.
+    """
+    structure = _viterbi_fast_structure()
+    source_idx = structure['source_idx']
+    log_trans = structure['log_trans']
+    state_idx = structure['state_idx']
+    log_emission = structure['log_emission']
+
+    prev = structure['log_starting'] + log_emission[observations[0]]
+    backpointers = np.empty((len(observations), 360), dtype=np.int16)
+    backpointers[0] = np.arange(360, dtype=np.int16)
+
+    for frame, observation in enumerate(observations[1:], start=1):
+        candidates = prev[source_idx] + log_trans
+        best_offsets = np.argmax(candidates, axis=1)
+        best_sources = source_idx[state_idx, best_offsets]
+        backpointers[frame] = best_sources
+        prev = candidates[state_idx, best_offsets] + log_emission[observation]
+
+    path = np.empty((len(observations),), dtype=np.int16)
+    path[-1] = int(np.argmax(prev))
+    for frame in range(len(observations) - 1, 0, -1):
+        path[frame - 1] = backpointers[frame, path[frame]]
+    return path
+
+
 def get_activation(audio, sr, model_capacity='full', center=True, step_size=10,
                    verbose=1):
     """
@@ -213,7 +314,8 @@ def get_activation(audio, sr, model_capacity='full', center=True, step_size=10,
 
 
 def predict(audio, sr, model_capacity='full',
-            viterbi=False, center=True, step_size=10, verbose=1):
+            viterbi=False, center=True, step_size=10, verbose=1,
+            viterbi_impl='legacy'):
     """
     Perform pitch estimation on given audio
 
@@ -229,6 +331,9 @@ def predict(audio, sr, model_capacity='full',
         :func:`~crepe.core.build_and_load_model`
     viterbi : bool
         Apply viterbi smoothing to the estimated pitch curve. False by default.
+    viterbi_impl : {'legacy', 'fast'}
+        Implementation used when `viterbi=True`. Defaults to the current
+        `hmmlearn` path (`legacy`).
     center : boolean
         - If `True` (default), the signal `audio` is padded so that frame
           `D[:, t]` is centered at `audio[t * hop_length]`.
@@ -258,7 +363,7 @@ def predict(audio, sr, model_capacity='full',
     confidence = activation.max(axis=1)
 
     if viterbi:
-        cents = to_viterbi_cents(activation)
+        cents = to_viterbi_cents_impl(activation, impl=viterbi_impl)
     else:
         cents = to_local_average_cents(activation)
 
@@ -272,7 +377,8 @@ def predict(audio, sr, model_capacity='full',
 
 def process_file(file, output=None, model_capacity='full', viterbi=False,
                  center=True, save_activation=False, save_plot=False,
-                 plot_voicing=False, step_size=10, verbose=True):
+                 plot_voicing=False, step_size=10, verbose=True,
+                 viterbi_impl='legacy'):
     """
     Use the input model to perform pitch estimation on the input file.
 
@@ -288,6 +394,8 @@ def process_file(file, output=None, model_capacity='full', viterbi=False,
         :func:`~crepe.core.build_and_load_model`
     viterbi : bool
         Apply viterbi smoothing to the estimated pitch curve. False by default.
+    viterbi_impl : {'legacy', 'fast'}
+        Implementation used when `viterbi=True`.
     center : boolean
         - If `True` (default), the signal `audio` is padded so that frame
           `D[:, t]` is centered at `audio[t * hop_length]`.
@@ -320,6 +428,7 @@ def process_file(file, output=None, model_capacity='full', viterbi=False,
         audio, sr,
         model_capacity=model_capacity,
         viterbi=viterbi,
+        viterbi_impl=viterbi_impl,
         center=center,
         step_size=step_size,
         verbose=1 * verbose)
@@ -363,4 +472,3 @@ def process_file(file, output=None, model_capacity='full', viterbi=False,
         imwrite(plot_file, (255 * image).astype(np.uint8))
         if verbose:
             print("CREPE: Saved the salience plot at {}".format(plot_file))
-
diff --git a/scripts/benchmark_viterbi.py b/scripts/benchmark_viterbi.py
new file mode 100644
index 0000000..eaff004
--- /dev/null
+++ b/scripts/benchmark_viterbi.py
@@ -0,0 +1,141 @@
+from __future__ import print_function
+
+import argparse
+import os
+import time
+
+import numpy as np
+from scipy.io import wavfile
+
+import crepe
+from crepe import core
+
+
+def time_call(fn, warmup, repeats):
+    last = None
+    for _ in range(warmup):
+        last = fn()
+    t0 = time.perf_counter()
+    for _ in range(repeats):
+        last = fn()
+    return ((time.perf_counter() - t0) * 1000.0 / repeats), last
+
+
+def synthetic_salience(frames, seed):
+    rng = np.random.RandomState(seed)
+    return rng.uniform(low=0.0, high=1.0, size=(frames, 360)).astype(np.float64)
+
+
+def has_weights(model_capacity):
+    return os.path.isfile(
+        os.path.join(os.path.dirname(core.__file__),
+                     'model-{}.h5'.format(model_capacity)))
+
+
+def benchmark_salience(salience, warmup, repeats):
+    results = []
+    for impl in ['legacy', 'fast']:
+        if impl == 'legacy':
+            try:
+                __import__('hmmlearn')
+            except ImportError:
+                results.append((impl, 'skipped', None))
+                continue
+        ms, _ = time_call(
+            lambda: core.to_viterbi_cents_impl(salience, impl=impl),
+            warmup,
+            repeats)
+        results.append((impl, 'ok', ms))
+    return results
+
+
+def benchmark_predict(audio, sr, model_capacity, warmup, repeats, verbose):
+    results = []
+    for impl in ['legacy', 'fast']:
+        if impl == 'legacy':
+            try:
+                __import__('hmmlearn')
+            except ImportError:
+                results.append((impl, 'skipped', None))
+                continue
+        ms, _ = time_call(
+            lambda: crepe.predict(
+                audio,
+                sr,
+                model_capacity=model_capacity,
+                viterbi=True,
+                viterbi_impl=impl,
+                verbose=verbose),
+            warmup,
+            repeats)
+        results.append((impl, 'ok', ms))
+    return results
+
+
+def print_results(title, results):
+    print('## {}'.format(title))
+    print('| Impl | Status | Mean time |')
+    print('|------|--------|-----------|')
+    for impl, status, ms in results:
+        value = '' if ms is None else '**{:.3f} ms**'.format(ms)
+        print('| `{}` | {} | {} |'.format(impl, status, value))
+    print()
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--frames', type=int, nargs='+', default=[512, 2048])
+    parser.add_argument('--warmup', type=int, default=2)
+    parser.add_argument('--repeats', type=int, default=10)
+    parser.add_argument('--seed', type=int, default=0)
+    parser.add_argument('--include-sweep', action='store_true')
+    parser.add_argument('--model-capacity', default='tiny',
+                        choices=['tiny', 'small', 'medium', 'large', 'full'])
+    parser.add_argument('--verbose', type=int, default=0)
+    args = parser.parse_args()
+
+    print('# CREPE Viterbi Benchmark')
+    print()
+    print('- `frames`: `{}`'.format(args.frames))
+    print('- `warmup`: `{}`'.format(args.warmup))
+    print('- `repeats`: `{}`'.format(args.repeats))
+    print('- `seed`: `{}`'.format(args.seed))
+    print('- `include_sweep`: `{}`'.format(args.include_sweep))
+    print('- `model_capacity`: `{}`'.format(args.model_capacity))
+    print()
+
+    for frames in args.frames:
+        salience = synthetic_salience(frames, seed=args.seed + frames)
+        print_results('Synthetic decoder core: {} frames'.format(frames),
+                      benchmark_salience(salience, args.warmup, args.repeats))
+
+    if not args.include_sweep:
+        return
+
+    if not has_weights(args.model_capacity):
+        print('> ⚠️ Sweep benchmark skipped: model weight file for `{}` is not '
+              'present.'.format(args.model_capacity))
+        return
+
+    try:
+        __import__('hmmlearn')
+    except ImportError:
+        print('> ⚠️ Sweep benchmark skipped: `hmmlearn` is not installed.')
+        return
+
+    sweep_path = os.path.join(os.path.dirname(__file__), '..', 'tests', 'sweep.wav')
+    sr, audio = wavfile.read(sweep_path)
+    activation = crepe.get_activation(
+        audio,
+        sr,
+        model_capacity=args.model_capacity,
+        verbose=args.verbose)
+    print_results('Sweep activation decoder core: {} frames'.format(len(activation)),
+                  benchmark_salience(activation, args.warmup, args.repeats))
+    print_results('Sweep full predict(): {} frames'.format(len(activation)),
+                  benchmark_predict(audio, sr, args.model_capacity,
+                                    args.warmup, args.repeats, args.verbose))
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tests/test_viterbi_impl.py b/tests/test_viterbi_impl.py
new file mode 100644
index 0000000..3e6ced8
--- /dev/null
+++ b/tests/test_viterbi_impl.py
@@ -0,0 +1,94 @@
+import numpy as np
+import pytest
+
+import crepe
+from crepe import cli
+from crepe import core
+
+
+def synthetic_salience(frames, seed=0):
+    rng = np.random.RandomState(seed)
+    return rng.uniform(low=0.0, high=1.0, size=(frames, 360)).astype(np.float64)
+
+
+def dense_reference_path(observations):
+    structure = core._viterbi_fast_structure()
+    states = 360
+    xx, yy = np.meshgrid(range(states), range(states))
+    transition = np.maximum(12 - abs(xx - yy), 0).astype(np.float64)
+    transition = transition / np.sum(transition, axis=1)[:, None]
+    log_transition = np.log(transition)
+    log_starting = structure['log_starting']
+    log_emission = structure['log_emission']
+
+    prev = log_starting + log_emission[observations[0]]
+    backpointers = np.empty((len(observations), states), dtype=np.int16)
+    backpointers[0] = np.arange(states, dtype=np.int16)
+
+    for frame, observation in enumerate(observations[1:], start=1):
+        candidates = prev[:, None] + log_transition
+        best_sources = np.argmax(candidates, axis=0)
+        backpointers[frame] = best_sources.astype(np.int16)
+        prev = candidates[best_sources, np.arange(states)] + log_emission[observation]
+
+    path = np.empty((len(observations),), dtype=np.int16)
+    path[-1] = int(np.argmax(prev))
+    for frame in range(len(observations) - 1, 0, -1):
+        path[frame - 1] = backpointers[frame, path[frame]]
+    return path
+
+
+class TestViterbiFast:
+    def test_fast_path_matches_dense_reference(self):
+        salience = synthetic_salience(64, seed=123)
+        observations = np.argmax(salience, axis=1)
+        fast = core._viterbi_path_fast(observations)
+        dense = dense_reference_path(observations)
+        np.testing.assert_array_equal(fast, dense)
+
+    def test_fast_cents_matches_legacy(self):
+        pytest.importorskip("hmmlearn")
+        salience = synthetic_salience(48, seed=321)
+        legacy = core.to_viterbi_cents_impl(salience, impl='legacy')
+        fast = core.to_viterbi_cents_impl(salience, impl='fast')
+        np.testing.assert_allclose(fast, legacy, rtol=0.0, atol=0.0)
+
+    def test_invalid_impl_raises(self):
+        salience = synthetic_salience(8, seed=7)
+        with pytest.raises(ValueError):
+            core.to_viterbi_cents_impl(salience, impl='nope')
+
+    def test_predict_routes_fast_impl(self, monkeypatch):
+        salience = synthetic_salience(16, seed=11)
+        monkeypatch.setattr(core, 'get_activation',
+                            lambda *args, **kwargs: salience)
+        _, frequency, confidence, activation = core.predict(
+            np.zeros((16000,), dtype=np.float32),
+            16000,
+            viterbi=True,
+            viterbi_impl='fast',
+            verbose=0)
+        cents = core.to_viterbi_cents_fast(salience)
+        expected_frequency = 10 * 2 ** (cents / 1200)
+        np.testing.assert_allclose(frequency, expected_frequency)
+        np.testing.assert_allclose(confidence, salience.max(axis=1))
+        np.testing.assert_allclose(activation, salience)
+
+    def test_cli_run_passes_viterbi_impl(self, monkeypatch, tmp_path):
+        wav_path = tmp_path / 'dummy.wav'
+        wav_path.write_bytes(b'RIFF')
+        captured = {}
+
+        def fake_process_file(file, **kwargs):
+            captured['file'] = file
+            captured['kwargs'] = kwargs
+
+        monkeypatch.setattr(cli, 'process_file', fake_process_file)
+        cli.run(
+            [str(wav_path)],
+            viterbi=True,
+            viterbi_impl='fast',
+            verbose=False)
+        assert captured['file'] == str(wav_path)
+        assert captured['kwargs']['viterbi'] is True
+        assert captured['kwargs']['viterbi_impl'] == 'fast'