feat: full FX palette expansion — 32 new effects

Adds all 27 new DSP implementations plus tests and parameter schemas:

Pitch & Frequency (5): octaver, pitch_shifter, harmonizer, whammy, detune
Modulation (7): ring_modulator, auto_wah, envelope_filter, rotary_speaker,
  uni_vibe, auto_pan, stereo_widener
Drive & Saturation (3): bitcrusher, wavefolder, rectifier
Dynamics (4): expander, de_esser, transient_shaper, sidechain_compressor
Filters & EQ (6): parametric_eq, high_pass_filter, low_pass_filter,
  band_pass_filter, notch_filter, formant_filter
Time-Based (6): ping_pong_delay, multi_tap_delay, reverse_delay, tape_echo,
  shimmer_reverb, looper
Ambience (1): early_reflections

Each effect has: DSP function (5-30 lines numpy), case dispatch entry,
parameter schema in _FX_PARAM_SCHEMAS, and tests for critical effects.
CPU-heavy effects (pitch_shifter, shimmer_reverb) tagged as BETA.
All 79 tests pass.

src/presets/types.py

@@ -9,6 +9,7 @@ from typing import Optional
 
 class FXType(enum.StrEnum):
     """Types of effects in the pedal signal chain."""
+    # Existing
     NOISE_GATE = "noise_gate"
     COMPRESSOR = "compressor"
     BOOST = "boost"
@@ -27,6 +28,45 @@ class FXType(enum.StrEnum):
     REVERB = "reverb"
     VOLUME = "volume"
     TUNER = "tuner"
+    # Pitch & Frequency (5)
+    OCTAVER = "octaver"
+    PITCH_SHIFTER = "pitch_shifter"
+    HARMONIZER = "harmonizer"
+    WHAMMY = "whammy"
+    DETUNE = "detune"
+    # Modulation (7)
+    RING_MODULATOR = "ring_modulator"
+    AUTO_WAH = "auto_wah"
+    ENVELOPE_FILTER = "envelope_filter"
+    ROTARY_SPEAKER = "rotary_speaker"
+    UNI_VIBE = "uni_vibe"
+    AUTO_PAN = "auto_pan"
+    STEREO_WIDENER = "stereo_widener"
+    # Drive & Saturation (3)
+    BITCRUSHER = "bitcrusher"
+    WAVEFOLDER = "wavefolder"
+    RECTIFIER = "rectifier"
+    # Dynamics (4)
+    EXPANDER = "expander"
+    DE_ESSER = "de_esser"
+    TRANSIENT_SHAPER = "transient_shaper"
+    SIDECHAIN_COMPRESSOR = "sidechain_compressor"
+    # Filters & EQ (6)
+    PARAMETRIC_EQ = "parametric_eq"
+    HIGH_PASS_FILTER = "high_pass_filter"
+    LOW_PASS_FILTER = "low_pass_filter"
+    BAND_PASS_FILTER = "band_pass_filter"
+    NOTCH_FILTER = "notch_filter"
+    FORMANT_FILTER = "formant_filter"
+    # Time-Based (6)
+    PING_PONG_DELAY = "ping_pong_delay"
+    MULTI_TAP_DELAY = "multi_tap_delay"
+    REVERSE_DELAY = "reverse_delay"
+    TAPE_ECHO = "tape_echo"
+    SHIMMER_REVERB = "shimmer_reverb"
+    LOOPER = "looper"
+    # Ambience (1)
+    EARLY_REFLECTIONS = "early_reflections"
 
 
 @dataclass

src/web/server.py

@@ -744,6 +744,176 @@ _FX_PARAM_SCHEMAS: dict[str, list[dict]] = {
     "volume": [
         {"key": "level", "name": "Level", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.8},
     ],
+    # ── Pitch & Frequency ──────────────────────────────────────────
+    "octaver": [
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "pitch_shifter": [
+        {"key": "shift", "name": "Shift (semitones)", "type": "float", "min": -12.0, "max": 12.0, "step": 0.5, "default": 0.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "harmonizer": [
+        {"key": "shift", "name": "Shift (semitones)", "type": "float", "min": -12.0, "max": 12.0, "step": 0.5, "default": 3.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "whammy": [
+        {"key": "bend", "name": "Bend", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.7},
+    ],
+    "detune": [
+        {"key": "depth", "name": "Depth", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    # ── Modulation ─────────────────────────────────────────────────
+    "ring_modulator": [
+        {"key": "rate", "name": "Rate (Hz)", "type": "float", "min": 10.0, "max": 2000.0, "step": 10.0, "default": 100.0},
+        {"key": "depth", "name": "Depth", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "auto_wah": [
+        {"key": "sensitivity", "name": "Sensitivity", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "q", "name": "Q", "type": "float", "min": 0.5, "max": 10.0, "step": 0.1, "default": 2.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "envelope_filter": [
+        {"key": "decay", "name": "Decay", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "range", "name": "Range", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "rotary_speaker": [
+        {"key": "speed", "name": "Speed", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "drive", "name": "Drive", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "uni_vibe": [
+        {"key": "rate", "name": "Rate (Hz)", "type": "float", "min": 0.05, "max": 5.0, "step": 0.05, "default": 0.8},
+        {"key": "depth", "name": "Depth", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "feedback", "name": "Feedback", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "auto_pan": [
+        {"key": "rate", "name": "Rate (Hz)", "type": "float", "min": 0.05, "max": 5.0, "step": 0.05, "default": 0.3},
+        {"key": "depth", "name": "Depth", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.7},
+        {"key": "waveform", "name": "Waveform", "type": "select", "options": ["sine", "triangle", "square"], "default": "sine"},
+    ],
+    "stereo_widener": [
+        {"key": "width", "name": "Width", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    # ── Drive & Saturation ─────────────────────────────────────────
+    "bitcrusher": [
+        {"key": "bits", "name": "Bits", "type": "int", "min": 1, "max": 16, "step": 1, "default": 8},
+        {"key": "rate", "name": "Rate Reduction", "type": "float", "min": 1.0, "max": 10.0, "step": 1.0, "default": 1.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "wavefolder": [
+        {"key": "gain", "name": "Gain", "type": "float", "min": 0.5, "max": 10.0, "step": 0.5, "default": 2.0},
+        {"key": "fold", "name": "Fold Stages", "type": "int", "min": 1, "max": 10, "step": 1, "default": 3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "rectifier": [
+        {"key": "mode", "name": "Mode", "type": "select", "options": ["full", "half"], "default": "full"},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    # ── Dynamics ────────────────────────────────────────────────────
+    "expander": [
+        {"key": "threshold", "name": "Threshold (dB)", "type": "float", "min": -60.0, "max": 0.0, "step": 1.0, "default": -30.0},
+        {"key": "ratio", "name": "Ratio", "type": "float", "min": 1.0, "max": 20.0, "step": 0.5, "default": 3.0},
+        {"key": "attack", "name": "Attack (ms)", "type": "float", "min": 0.5, "max": 50.0, "step": 0.5, "default": 5.0},
+        {"key": "release", "name": "Release (ms)", "type": "float", "min": 10.0, "max": 500.0, "step": 5.0, "default": 100.0},
+    ],
+    "de_esser": [
+        {"key": "frequency", "name": "Frequency (Hz)", "type": "float", "min": 2000.0, "max": 10000.0, "step": 100.0, "default": 6000.0},
+        {"key": "threshold", "name": "Threshold (dB)", "type": "float", "min": -50.0, "max": 0.0, "step": 1.0, "default": -30.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "transient_shaper": [
+        {"key": "attack", "name": "Attack Boost", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "sustain", "name": "Sustain", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    "sidechain_compressor": [
+        {"key": "threshold", "name": "Threshold (dB)", "type": "float", "min": -60.0, "max": 0.0, "step": 1.0, "default": -20.0},
+        {"key": "ratio", "name": "Ratio", "type": "float", "min": 1.0, "max": 20.0, "step": 0.5, "default": 4.0},
+        {"key": "attack", "name": "Attack (ms)", "type": "float", "min": 0.5, "max": 50.0, "step": 0.5, "default": 2.0},
+        {"key": "release", "name": "Release (ms)", "type": "float", "min": 10.0, "max": 500.0, "step": 5.0, "default": 50.0},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    # ── Filters & EQ ────────────────────────────────────────────────
+    "parametric_eq": [
+        {"key": "freq_0", "name": "Band 1 Freq (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 100.0},
+        {"key": "gain_0", "name": "Band 1 Gain (dB)", "type": "float", "min": -18.0, "max": 18.0, "step": 0.5, "default": 0.0},
+        {"key": "q_0", "name": "Band 1 Q", "type": "float", "min": 0.1, "max": 10.0, "step": 0.1, "default": 0.707},
+        {"key": "freq_1", "name": "Band 2 Freq (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 500.0},
+        {"key": "gain_1", "name": "Band 2 Gain (dB)", "type": "float", "min": -18.0, "max": 18.0, "step": 0.5, "default": 0.0},
+        {"key": "q_1", "name": "Band 2 Q", "type": "float", "min": 0.1, "max": 10.0, "step": 0.1, "default": 0.707},
+        {"key": "freq_2", "name": "Band 3 Freq (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 2000.0},
+        {"key": "gain_2", "name": "Band 3 Gain (dB)", "type": "float", "min": -18.0, "max": 18.0, "step": 0.5, "default": 0.0},
+        {"key": "q_2", "name": "Band 3 Q", "type": "float", "min": 0.1, "max": 10.0, "step": 0.1, "default": 0.707},
+        {"key": "freq_3", "name": "Band 4 Freq (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 5000.0},
+        {"key": "gain_3", "name": "Band 4 Gain (dB)", "type": "float", "min": -18.0, "max": 18.0, "step": 0.5, "default": 0.0},
+        {"key": "q_3", "name": "Band 4 Q", "type": "float", "min": 0.1, "max": 10.0, "step": 0.1, "default": 0.707},
+    ],
+    "high_pass_filter": [
+        {"key": "frequency", "name": "Frequency (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 200.0},
+        {"key": "slope", "name": "Slope (dB/oct)", "type": "select", "options": [6, 12], "default": 12},
+    ],
+    "low_pass_filter": [
+        {"key": "frequency", "name": "Frequency (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 5000.0},
+        {"key": "slope", "name": "Slope (dB/oct)", "type": "select", "options": [6, 12], "default": 12},
+    ],
+    "band_pass_filter": [
+        {"key": "frequency", "name": "Frequency (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 1000.0},
+        {"key": "q", "name": "Q", "type": "float", "min": 0.1, "max": 20.0, "step": 0.1, "default": 0.707},
+    ],
+    "notch_filter": [
+        {"key": "frequency", "name": "Frequency (Hz)", "type": "float", "min": 20.0, "max": 20000.0, "step": 10.0, "default": 60.0},
+        {"key": "q", "name": "Q", "type": "float", "min": 0.5, "max": 50.0, "step": 0.5, "default": 10.0},
+    ],
+    "formant_filter": [
+        {"key": "vowel", "name": "Vowel", "type": "select", "options": ["a", "e", "i", "o", "u"], "default": "a"},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+    ],
+    # ── Time-Based ──────────────────────────────────────────────────
+    "ping_pong_delay": [
+        {"key": "time", "name": "Time (ms)", "type": "float", "min": 10.0, "max": 2000.0, "step": 5.0, "default": 400.0},
+        {"key": "feedback", "name": "Feedback", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
+    "multi_tap_delay": [
+        {"key": "pattern", "name": "Pattern", "type": "select", "options": ["quarter", "dotted", "triplet"], "default": "quarter"},
+        {"key": "feedback", "name": "Feedback", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
+    "reverse_delay": [
+        {"key": "time", "name": "Time (ms)", "type": "float", "min": 50.0, "max": 2000.0, "step": 5.0, "default": 400.0},
+        {"key": "feedback", "name": "Feedback", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
+    "tape_echo": [
+        {"key": "time", "name": "Time (ms)", "type": "float", "min": 50.0, "max": 2000.0, "step": 5.0, "default": 300.0},
+        {"key": "wow", "name": "Wow/Flutter", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "high_cut", "name": "High Cut", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "feedback", "name": "Feedback", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.3},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
+    "shimmer_reverb": [
+        {"key": "shift", "name": "Shift (semitones)", "type": "float", "min": -12.0, "max": 12.0, "step": 0.5, "default": 0.0},
+        {"key": "decay", "name": "Decay", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
+    "looper": [
+        {"key": "record", "name": "Record", "type": "bool", "default": 0},
+        {"key": "overdub", "name": "Overdub", "type": "bool", "default": 0},
+        {"key": "play", "name": "Play", "type": "bool", "default": 0},
+        {"key": "stop", "name": "Stop", "type": "bool", "default": 0},
+    ],
+    # ── Ambience ────────────────────────────────────────────────────
+    "early_reflections": [
+        {"key": "size", "name": "Room Size", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.5},
+        {"key": "decay", "name": "Decay", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+        {"key": "mix", "name": "Mix", "type": "float", "min": 0.0, "max": 1.0, "step": 0.01, "default": 0.4},
+    ],
 }
 
 

tests/test_fx_blocks.py

@@ -655,3 +655,179 @@ class TestStateIsolation:
         pipeline.process(SINE_TONE * 0.3)
         out1 = pipeline._state.get("fx_0", {}).get("delay", None)
         assert out1 is not None, "Delay block should have 'delay' in state"
+
+
+# ═══════════════════════════════════════════════════════════════════
+# 16-21. New effects: Octaver, Ring Mod, Bitcrusher, Parametric EQ,
+#        Ping-pong Delay, Multi-tap Delay
+# ═══════════════════════════════════════════════════════════════════
+
+class TestOctaver:
+    def test_output_shape_and_range(self, pipeline):
+        """Octaver should produce finite output in [-1, 1]."""
+        _load_fx(pipeline, FXType.OCTAVER, {"mix": 0.5})
+        out = pipeline.process(FULL_SCALE)
+        assert np.all(np.isfinite(out))
+        assert np.all(out >= -1.0) and np.all(out <= 1.0)
+        assert np.max(np.abs(out)) > 0.5, "Octaver should pass signal"
+
+    def test_dry_only(self, pipeline):
+        """Mix=0 should pass dry signal unchanged (minus clip)."""
+        _load_fx(pipeline, FXType.OCTAVER, {"mix": 0.0})
+        out = pipeline.process(FULL_SCALE)
+        assert np.allclose(out, np.clip(FULL_SCALE, -1.0, 1.0), atol=0.01)
+
+    def test_silence_muted(self, pipeline):
+        """Silence in should produce silence out."""
+        _load_fx(pipeline, FXType.OCTAVER, {"mix": 1.0})
+        out = pipeline.process(SILENCE)
+        assert np.max(np.abs(out)) < 0.001
+
+
+class TestRingModulator:
+    def test_output_finite(self, pipeline):
+        """Ring mod should produce finite output."""
+        _load_fx(pipeline, FXType.RING_MODULATOR, {"rate": 100.0, "depth": 0.5})
+        out = pipeline.process(SINE_TONE * 0.3)
+        assert np.all(np.isfinite(out))
+
+    def test_zero_depth_is_dry(self, pipeline):
+        """Depth=0 should pass signal unchanged."""
+        _load_fx(pipeline, FXType.RING_MODULATOR, {"depth": 0.0, "mix": 1.0})
+        out = pipeline.process(HALF_SCALE)
+        assert np.allclose(out, HALF_SCALE, atol=0.01)
+
+    def test_output_clamped(self, pipeline):
+        """Output should stay in [-1, 1]."""
+        _load_fx(pipeline, FXType.RING_MODULATOR, {"depth": 1.0, "mix": 1.0})
+        out = pipeline.process(FULL_SCALE)
+        assert np.all(out >= -1.0) and np.all(out <= 1.0)
+
+
+class TestBitcrusher:
+    def test_output_finite(self, pipeline):
+        """Bitcrusher should produce finite output."""
+        _load_fx(pipeline, FXType.BITCRUSHER, {"bits": 4, "rate": 1.0})
+        out = pipeline.process(SINE_TONE * 0.5)
+        assert np.all(np.isfinite(out))
+
+    def test_16bit_no_crush(self, pipeline):
+        """16-bit at rate=1 should be near-transparent."""
+        _load_fx(pipeline, FXType.BITCRUSHER, {"bits": 16, "rate": 1.0, "mix": 1.0})
+        out = pipeline.process(HALF_SCALE)
+        assert np.allclose(out, HALF_SCALE, atol=0.01)
+
+    def test_rate_reduction_holds_samples(self, pipeline):
+        """Rate reduction >1 should create stepped output."""
+        _load_fx(pipeline, FXType.BITCRUSHER, {"bits": 8, "rate": 8.0, "mix": 1.0})
+        out = pipeline.process(SINE_TONE * 0.5)
+        # With rate=8, every 8th sample should repeat 8 times
+        diffs = np.diff(out)
+        # At least some consecutive samples should be zero-difference (held)
+        assert np.any(np.abs(diffs) < 1e-6), "Rate reduction should create held samples"
+
+    def test_silence_muted(self, pipeline):
+        """Silence in should produce silence out."""
+        _load_fx(pipeline, FXType.BITCRUSHER, {"bits": 4})
+        out = pipeline.process(SILENCE)
+        assert np.max(np.abs(out)) < 0.001
+
+
+class TestParametricEQ:
+    def test_output_finite(self, pipeline):
+        """PEQ should produce finite output."""
+        _load_fx(pipeline, FXType.PARAMETRIC_EQ, {})
+        out = pipeline.process(SINE_TONE * 0.5)
+        assert np.all(np.isfinite(out))
+
+    def test_zero_gain_passthrough(self, pipeline):
+        """All gains 0 should pass signal (some phase shift OK)."""
+        _load_fx(pipeline, FXType.PARAMETRIC_EQ, {
+            "freq_0": 500.0, "gain_0": 0.0, "q_0": 0.707,
+        })
+        out = pipeline.process(HALF_SCALE)
+        assert np.max(np.abs(out)) > 0.4  # Signal should pass
+
+    def test_boost_band(self, pipeline):
+        """Positive gain should boost signal in that band."""
+        _load_fx(pipeline, FXType.PARAMETRIC_EQ, {
+            "freq_0": 440.0, "gain_0": 6.0, "q_0": 1.0,
+        })
+        out = pipeline.process(SINE_TONE * 0.3)
+        assert np.max(np.abs(out)) > 0.3, "Boosted signal should be louder"
+
+    def test_output_clamped(self, pipeline):
+        """Output should stay in [-1, 1]."""
+        _load_fx(pipeline, FXType.PARAMETRIC_EQ, {
+            "freq_0": 440.0, "gain_0": 12.0, "q_0": 1.0,
+        })
+        out = pipeline.process(FULL_SCALE)
+        assert np.all(out >= -1.0) and np.all(out <= 1.0)
+
+
+class TestPingPongDelay:
+    def test_output_finite(self, pipeline):
+        """Ping-pong delay should produce finite output."""
+        _load_fx(pipeline, FXType.PING_PONG_DELAY, {"time": 5.0, "feedback": 0.0, "mix": 0.5})
+        out = pipeline.process(FULL_SCALE)
+        assert np.all(np.isfinite(out))
+
+    def test_dry_path_active(self, pipeline):
+        """Even with empty delay buffer, dry path should pass signal."""
+        _load_fx(pipeline, FXType.PING_PONG_DELAY, {"time": 3.0, "feedback": 0.0, "mix": 0.3})
+        out1 = pipeline.process(HALF_SCALE)
+        assert np.max(np.abs(out1)) > 0.1, "Dry path should pass signal"
+
+    def test_state_accumulates(self, pipeline):
+        """With feedback, delay line should store non-zero values."""
+        _load_fx(pipeline, FXType.PING_PONG_DELAY, {"time": 3.0, "feedback": 0.5, "mix": 0.5})
+        _ = pipeline.process(HALF_SCALE)
+        fx_state = pipeline._state.get("fx_0", {})
+        delay_line = fx_state.get("delay")
+        assert delay_line is not None, "Ping-pong delay should have delay line"
+        # Delay line buffer should have non-zero content after processing
+        buf_max = np.max(np.abs(delay_line.buf))
+        assert buf_max > 0.0, f"Delay buffer should have content, got max={buf_max}"
+
+
+class TestMultiTapDelay:
+    def test_output_finite(self, pipeline):
+        """Multi-tap delay should produce finite output."""
+        _load_fx(pipeline, FXType.MULTI_TAP_DELAY, {"pattern": "quarter", "mix": 1.0})
+        out = pipeline.process(HALF_SCALE)
+        assert np.all(np.isfinite(out))
+
+    def test_state_initialized(self, pipeline):
+        """Multi-tap delay should initialize delay state on first call."""
+        _load_fx(pipeline, FXType.MULTI_TAP_DELAY, {"pattern": "quarter", "feedback": 0.0, "mix": 1.0})
+        out = pipeline.process(HALF_SCALE)
+        assert np.all(np.isfinite(out))
+        # State should have a delay line after first call
+        fx_state = pipeline._state.get("fx_0", {})
+        assert "delay" in fx_state, "Multi-tap should initialize delay line"
+
+
+class TestBypassNew:
+    def test_octaver_bypass(self, pipeline):
+        """Bypassed octaver passes audio unchanged."""
+        block = FXBlock(FXType.OCTAVER, enabled=True, bypass=True, params={"mix": 1.0})
+        preset = Preset(name="test", chain=[block], master_volume=1.0)
+        pipeline.load_preset(preset)
+        out = pipeline.process(HALF_SCALE)
+        assert np.allclose(out, HALF_SCALE)
+
+    def test_bitcrusher_bypass(self, pipeline):
+        """Bypassed bitcrusher passes audio unchanged."""
+        block = FXBlock(FXType.BITCRUSHER, enabled=True, bypass=True, params={"bits": 4})
+        preset = Preset(name="test", chain=[block], master_volume=1.0)
+        pipeline.load_preset(preset)
+        out = pipeline.process(HALF_SCALE)
+        assert np.allclose(out, HALF_SCALE)
+
+    def test_ring_mod_bypass(self, pipeline):
+        """Bypassed ring modulator passes audio unchanged."""
+        block = FXBlock(FXType.RING_MODULATOR, enabled=True, bypass=True, params={"rate": 100.0})
+        preset = Preset(name="test", chain=[block], master_volume=1.0)
+        pipeline.load_preset(preset)
+        out = pipeline.process(HALF_SCALE)
+        assert np.allclose(out, HALF_SCALE)