shorepine · dpwe · Apr 18, 2026 · Apr 18, 2026 · Apr 18, 2026 · Apr 18, 2026
diff --git a/amy/__init__.py b/amy/__init__.py
@@ -138,7 +138,7 @@ def str_of_int(arg):
 _KW_MAP_LIST = [   # Order matters because patch_string must come last.
     ('osc', 'vI'), ('wave', 'wI'), ('note', 'nF'), ('vel', 'lF'), ('amp', 'aC'), ('freq', 'fC'), ('duty', 'dC'), 
     ('feedback', 'bF'), ('time', 'tI'),  ('reset', 'SI'), ('phase', 'PF'), ('pan', 'QC'), ('client', 'gI'), 
-    ('volume', 'VF'), ('pitch_bend', 'sF'), ('filter_freq', 'FC'), ('resonance', 'RF'),
+    ('volume', 'VL'), ('pitch_bend', 'sF'), ('filter_freq', 'FC'), ('resonance', 'RF'),
     ('bp0', 'AL'), ('bp1', 'BL'),
     ('eg0', 'AL'), ('eg1', 'BL'),  # Aliases for bp0 and bp1
     ('eg0_type', 'TI'), ('eg1_type', 'XI'), ('debug', 'DI'), ('chained_osc', 'cI'),
@@ -150,7 +150,7 @@ def str_of_int(arg):
     ('to_synth', 'itI'), ('grab_midi_notes', 'imI'),  ('synth_delay', 'idI'),
     ('preset', 'pI'), ('num_partials', 'pI'), # note aliasing
     ('start_sample', 'zSL'), ('stop_sample', 'zOI'),
-    ('midi_cc', 'icL'),
+    ('midi_cc', 'icL'), ('bus', 'yI'),
     ('patch_string', 'uS'),  # patch_string MUST be last because we can't identify when it ends except by end-of-message.
 ]
 _KW_PRIORITY = {k: i for i, (k, _) in enumerate(_KW_MAP_LIST)}   # Maps each key to its index within _KW_MAP_LIST.
@@ -356,8 +356,8 @@ def b64(b):
     def b64(b):
         return ubinascii.b2a_base64(b)[:-1]
 
-def start_sample(preset=0, bus=1,  max_frames=0, midinote=60, loopstart=0, loopend=0):
-    s = "%d,%d,%d,%d,%d,%d" % (preset, bus, max_frames, midinote, loopstart, loopend)
+def start_sample(preset=0, source=SAMPLE_FROM_OUTPUT,  max_frames=0, midinote=60, loopstart=0, loopend=0):
+    s = "%d,%d,%d,%d,%d,%d" % (preset, source, max_frames, midinote, loopstart, loopend)
     send(start_sample=s)
 
 def stop_sample():

diff --git a/amy/constants.py b/amy/constants.py
@@ -15,8 +15,10 @@
 AMY_PCM_TYPE_FILE=1
 AMY_PCM_TYPE_MEMORY=2
 PCM_FILE_BUFFER_MULT=8
-AMY_BUS_OUTPUT=1
-AMY_BUS_AUDIO_IN=2
+SAMPLE_FROM_OUTPUT=1
+SAMPLE_FROM_AUDIO_IN=2
+AMY_NUM_BUSES=4
+AMY_DEFAULT_BUS=0
 AMY_MAX_CORES=2
 AMY_MAX_CHANNELS=2
 AMY_NCHANS=2
@@ -37,7 +39,7 @@
 REVERB_DEFAULT_XOVER_HZ=3000.0
 ECHO_DEFAULT_LEVEL=0
 ECHO_DEFAULT_DELAY_MS=500.
-ECHO_DEFAULT_MAX_DELAY_MS=743.
+ECHO_DEFAULT_MAX_DELAY_MS=743.039
 ECHO_DEFAULT_FEEDBACK=0
 ECHO_DEFAULT_FILTER_COEF=0
 AMY_SEQUENCER_PPQ=48

diff --git a/amy/fm.py b/amy/fm.py
@@ -238,7 +238,7 @@ def send_to_AMY(self, reset=True):
         # Set up each operator.
         last_release_time = 0
         last_release_value = 0
-        # Oscs: 0 is algo, 1 is pitch LFO, 2 is amp LFO, 3-8 are ops 1-6
+        # Oscs: 0 is algo, 1 is LFO, 2-7 are ops 1-6
         main_osc = 0
         lfo_osc = 1
         # The osc of op0 (they go up from here)
@@ -251,14 +251,14 @@ def send_to_AMY(self, reset=True):
                 amp_times[2], t(amp_levels[2]), amp_times[3], t(amp_levels[3]),
                 amp_times[4], t(amp_levels[4])
             )
-            oscbpfmt = "%d,%s/%d,%s/%d,%s/%d,%s/%d,%s" % (
-                amp_times[0], t(amp_levels[0]), amp_times[1], t(amp_levels[1]),
-                amp_times[2], t(amp_levels[2]), amp_times[3], t(amp_levels[3]),
-                amp_times[4], t(amp_levels[4])
-            )
             if(amp_times[4] > last_release_time):
                 last_release_time = amp_times[4]
                 last_release_value = amp_levels[4]
+            #oscbpfmt = "%d,%s/%d,%s/%d,%s/%d,%s/%d,%s" % (
+            #    amp_times[0], t(amp_levels[0]), amp_times[1], t(amp_levels[1]),
+            #    amp_times[2], t(amp_levels[2]), amp_times[3], t(amp_levels[3]),
+            #    amp_times[4], t(amp_levels[4])
+            #)
             #print("osc %d (op %d) freq %.6f ratio %d env %s amp %.6f amp_mod %d" % \
             #      (osc_num, osc.op_num_from_0, osc.frequency, osc.freq_is_ratio, oscbpfmt,
             #       osc.op_amp, osc.ampmodsens))
@@ -270,7 +270,7 @@ def send_to_AMY(self, reset=True):
                 args["ratio"] = t(osc.frequency)
             else:
                 args["freq"] = t(osc.frequency)
-            # TODO: we xignore intensity of amp mod sens, just on/off
+            # TODO: we ignore intensity of amp mod sens, just on/off
             args.update({"mod_source": lfo_osc, "amp": "%s,0,0,1,0,%s" % (t(osc.op_amp), t(self.amp_lfo_amp * (osc.ampmodsens > 0)))})
 
             # We are _NOT_ updating operators with pitch bp, per dan tuesday 7/5 morning (but not monday 7/4 morning)

diff --git a/amy/test.py b/amy/test.py
@@ -1063,7 +1063,7 @@ def run(self):
 class TestSample(AmyTest):
 
   def run(self):
-    amy.start_sample(preset=1024,bus=1,max_frames=22050, midinote=60)
+    amy.start_sample(preset=1024, source=amy.SAMPLE_FROM_OUTPUT, max_frames=22050, midinote=60)
     amy.send(time=0, synth=1, num_voices=4, patch=20)
     amy.send(time=50, synth=1, note=48, vel=1)
     amy.send(time=150, synth=1, note=60, vel=1)
@@ -1265,6 +1265,22 @@ def run(self):
     amy.send(time=750, synth=1, note=48, vel=1)
     amy.send(time=950, synth=1, vel=0)
 
+
+class TestBuses(AmyTest):
+  """You can assign synths to different buses to get independent FX."""
+
+  def run(self):
+    amy.send(time=0, synth=1, num_voices=4, patch=22, bus=0, pan=0.2)  # A37 Pizzicato
+    amy.send(time=0, bus=0, reverb=1, echo=0)
+    amy.send(time=0, synth=2, num_voices=4, patch=22, bus=1, pan=0.8)
+    amy.send(time=0, bus=1, reverb=0, echo='1,100,,0.5,0.5')
+    amy.send(time=0, volume='2,0.5')  # Mixdown for buses 0 and 1.
+    amy.send(time=100, synth=1, note=60, vel=5)
+    amy.send(time=300, synth=2, note=63, vel=5)
+    amy.send(time=500, synth=1, note=67, vel=5)
+    amy.send(time=700, synth=2, note=70, vel=5)
+
+
 def main(argv):
   if len(argv) > 1 and argv[1] == 'quiet':
     quiet = True

diff --git a/docs/api.md b/docs/api.md
@@ -220,6 +220,7 @@ A note on list parameters:  When an argument is a list of parameters, you can in
 | `in`   | `oscs_per_voice`  | `oscs_per_voice`  | >0  | Reserve this many oscs for each voice.  Needed when initializing a synth (or voice) withouth an initial patch. Setting `oscs_per_voice` on an existing synth resets all oscs to their default state. |
 | `im`   | `grab_midi_notes` | `grab_midi_notes` | 0/1 | Use `amy.send(synth=CHANNEL, grab_midi_notes=0)` to prevent the default direct forwarding of MIDI note-on/offs to synth CHANNEL. |
 | `ip`   | `pedal` | `pedal` | int | Non-zero means pedal is down (i.e., sustain).  Must be used with `synth`. |
+| `iy`   | `bus`   | `bus`   | int | Bus onto which the synth outputs are added (synonym for `y`). |
 | `K`    | `patch_number` | `patch` | uint 0-X | Apply a saved or user patch to a specified synth or voice. |
 | `r`    | `voices[]` | `voices` | int[,int] | Comma separated list of voices to send message to, or load patch into. |
 | `u`    | **TODO**| `patch_string` | string | Provide AMY message to define up to 32 patches in RAM with ID numbers (1024-1055) provided via `patch_number`, or directly configure a `synth`. |
@@ -249,6 +250,7 @@ A note on list parameters:  When an argument is a list of parameters, you can in
 | `R`    | `resonance` | `resonance` | float | Q factor of variable filter, 0.5-16.0. default 0.7 |
 | `T`    | `eg_type[0]` | `eg0_type` | uint 0-3 | Type for Envelope Generator 0 - 0: Normal (RC-like) / 1: Linear / 2: DX7-style / 3: True exponential. |
 | `X`    | `eg_type[1]` | `eg1_type` | uint 0-3 | Type for Envelope Generator 1 - 0: Normal (RC-like) / 1: Linear / 2: DX7-style / 3: True exponential. |
+| `y`    | bus        | `bus` | int   | Bus that this osc gets added onto (default 0) |
 | `l`    | `velocity` | `vel` | float | Note on velocity. Use to start an envelope or set amplitude |
 
 ### CtrlCoefs
@@ -269,7 +271,7 @@ These per-oscillator parameters use [CtrlCoefs](synth.md) notation
 | ------ | -------- | ---------- | ----------  | ------------------------------------- |
 | `z`    | **TODO**| `load_sample` | uint x 6 | Signal to start loading sample. preset number, length(frames), samplerate, channels, midinote, loopstart, loopend. All subsequent messages are base64 encoded WAVE-style frames of audio until `length` is reached. Set `preset` and `length=0` to unload a sample from RAM. |
 | `zF`   | **TODO**| `disk_sample` | uint,string,uint | Set a PCM preset to play live from a WAV filename on AMY host disk. Params: preset number, filename, midinote. See `hooks` for reading files on host disk. **Only one file sample can be played at once per preset number. Use multiple presets if you want polyphony from a single sample.** |
-| `zS`   | **TODO**| `start_sample` | uint x 6 | Start sampling to a stereo PCM preset from bus. Params: preset number,  bus, max length in frames, midinote, loopstart, loopend. bus = 1 is AMY mixed output. bus = 2 is AUDIO_IN0 + 1.  Will sample until max length is reached, `stop_sample` is issued, or a new `start_sample` is issued. | 
+| `zS`   | **TODO**| `start_sample` | uint x 6 | Start sampling to a stereo PCM preset from source. Params: preset number, source, max length in frames, midinote, loopstart, loopend. source = 1 is AMY mixed output. source = 2 is AUDIO_IN0 + 1.  Will sample until max length is reached, `stop_sample` is issued, or a new `start_sample` is issued. | 
 | `zO`   | **TODO**| `stop_sample` | uint | Stop sampling. Does nothing if no sampling active. param ignored. | 
 
 ### WAVETABLE wave type
@@ -284,20 +286,31 @@ These per-oscillator parameters use [CtrlCoefs](synth.md) notation
 - Each wavetable preset is expected to be one 64-cycle table (normally `16384` samples total, `256` samples per cycle).
 - `duty` crossfades across the 64 cycles inside the selected wavetable preset.
 
+### Per-bus Effects
+
+Each of the `y` buses has separate effects units.  You set their parameters with commands such as `amy.send(bus=0, reverb=1)` (or `y0h1`).
+
+The final mixdown of the buses onto the AMY output is controlled by one value per bus passed to the `volume` (`V`) command.
+
+Default AMY has 4 buses, 0..3.  If the bus (`y`) is not specified for one of these commands, it defaults to 0.
+
+| Wire code   | C `amy_event` | Python / JS   | Type-range  | Notes                                 |
+| ------ | -------- | ---------- | ----------  | ------------------------------------- |
+| `h`    | `reverb_level, reverb_liveness, reverb_damping, reverb_xover_hz` | `reverb` | float[,float,float,float] | Reverb parameters -- level, liveness, damping, xover: Level is for output mix;
+| `k`    | `chorus_level, chorus_max_delay, chorus_lfo_freq, chorus_depth` | `chorus` | float[,float,float,float] | Chorus parameters -- level, delay, freq, depth: Level is for output mix (0 to turn off); delay is max in samples (320); freq is LFO rate in Hz (0.5); depth is proportion of max delay (0.5). |
+| `M`    | `echo_level, echo_delay_ms, echo_max_delay_ms, echo_feedback, echo_filter_coef` | `echo` | float[,int,int,float,float] | Echo parameters --  level, delay_ms, max_delay_ms, feedback, filter_coef (-1 is HPF, 0 is flat, +1 is LPF). |
+| `x`    | `eq_l, eq_m, eq_h` |`eq` | float,float,float | Equalization in dB low (~800Hz) / med (~2500Hz) / high (~7500Gz) -15 to 15. 0 is off. default 0. |
+
 ### Other
 
 | Wire code   | C `amy_event` | Python / JS   | Type-range  | Notes                                 |
 | ------ | -------- | ---------- | ----------  | ------------------------------------- |
 | `H`    | `sequence[3]` | `sequence` | int,int,int | Tick offset, period, tag for sequencing | 
-| `h`    | `reverb_level, reverb_liveness, reverb_damping, reverb_xover_hz` | `reverb` | float[,float,float,float] | Reverb parameters -- level, liveness, damping, xover: Level is for output mix; liveness controls decay time, 1 = longest, default 0.85; damping is extra decay of high frequencies, default 0.5; xover is damping crossover frequency, default 3000 Hz. |
 | `j`    | `tempo` | `tempo`  | float | The tempo (BPM, quarter notes) of the sequencer. Defaults to 108.0. |
-| `k`    | `chorus_level, chorus_max_delay, chorus_lfo_freq, chorus_depth` | `chorus` | float[,float,float,float] | Chorus parameters -- level, delay, freq, depth: Level is for output mix (0 to turn off); delay is max in samples (320); freq is LFO rate in Hz (0.5); depth is proportion of max delay (0.5). |
-| `M`    | `echo_level, echo_delay_ms, echo_max_delay_ms, echo_feedback, echo_filter_coef` | `echo` | float[,int,int,float,float] | Echo parameters --  level, delay_ms, max_delay_ms, feedback, filter_coef (-1 is HPF, 0 is flat, +1 is LPF). |
 | `N`    | `latency_ms`| `latency_ms` | uint | Sets latency in ms. default 0 (see LATENCY) |
 | `s`    | `pitch_bend` | `pitch_bend` | float | Sets the global pitch bend, by default modifying all note frequencies by (fractional) octaves up or down |
 | `t`    | `time` | `time` | uint | Request playback time relative to some fixed start point on your host, in ms. Allows precise future scheduling. |
-| `V`    | `volume`| `volume` | float 0-10 | Volume knob for entire synth, default 1.0 |
-| `x`    | `eq_l, eq_m, eq_h` |`eq` | float,float,float | Equalization in dB low (~800Hz) / med (~2500Hz) / high (~7500Gz) -15 to 15. 0 is off. default 0. |
+| `V`    | `volume`| `volume` | float, float, ...  | Volume knob for each bus in the final mixdown, default 1.0 |
 | `g`    | `client` | `client` | uint | Client number for Alles distributed synthesis. |
 | `W`    | `external_channel` | `external_channel` | uint | External channel routing (used by Tulip for CV output). |
 | `D`    | **TODO** | `debug`  |  uint, 2-4  | 2 shows queue sample, 3 shows oscillator data, 4 shows modified oscillator. Will interrupt audio! |

diff --git a/docs/synth.md b/docs/synth.md
@@ -376,12 +376,12 @@ amy.send(osc=1, wave=amy.PCM_RIGHT, preset=1025, pan=1, note=60, vel=1)
 
 ### Sampling
 
-AMY can also sample directly into a PCM memory buffer from a `bus`. [A bus in AMY is a work in progress](https://github.com/shorepine/amy/issues/114) but for now we support two stereo buses: `bus=1` is the final AMY output and `bus=2` is just `AUDIO_IN0` and `AUDIO_IN1`. To start sampling to a PCM preset, use `start_sample`:
+AMY can also sample directly into a PCM memory buffer.  We support two stereo sampling sources: `source=amy.SAMPLE_FROM_OUTPUT` is the final AMY output and `source=amy.SAMPLE_FROM_AUDIO_IN` is just `AUDIO_IN0` and `AUDIO_IN1`. To start sampling to a PCM preset, use `start_sample`:
 
 ```python
-amy.start_sample(preset=1024, bus=0, max_frames=44100)  # sample for one second
+amy.start_sample(preset=1024, source=amy.SAMPLE_FROM_AUDIO_IN, max_frames=44100)  # sample for one second
 amy.stop_sample() # stop all sampling, not needed if using max_frames
-amy.start_sample(preset=1024, bus=1, max_frames=11025, midinote=60) # set base midi note, looping, too
+amy.start_sample(preset=1024, source=amy.SAMPLE_FROM_OUTPUT, max_frames=11025, midinote=60) # set base midi note, looping, too
 amy.send(osc=0, wave=amy.PCM_LEFT, preset=1024, pan=0, note=72, vel=1) # play back AUDIO_IN sample an octave higher
 amy.send(osc=1, wave=amy.PCM_RIGHT, preset=1024, pan=1, note=72, vel=1) 
 ```

diff --git a/src/amy-example.c b/src/amy-example.c
@@ -62,9 +62,10 @@ void test_patch_set() {
     e.wave = SINE;
     amy_add_event(&e);
 
-    // Change the global volume.
+    // Change the global volume for bus 0.
     e = amy_default_event();
-    e.volume = 2.0f;
+    int bus = 0;
+    e.volume[bus] = 2.0f;
     amy_add_event(&e);
 }