diff --git a/artiq/wavesynth/compute_samples.py b/artiq/wavesynth/compute_samples.py
index 834740379..5b91053fb 100644
--- a/artiq/wavesynth/compute_samples.py
+++ b/artiq/wavesynth/compute_samples.py
@@ -25,7 +25,7 @@ class SplinePhase:
 
     def set_coefficients(self, c):
         self.c = self.c[0:1] + c[1:]
-        self.c0 = self.c[0]
+        self.c0 = c[0]
 
     def clear(self):
         self.c[0] = 0.0
@@ -55,21 +55,136 @@ class Wave:
         return self.bias.next() + self.dds.next()
 
 
-if __name__ == "__main__":
+class TriggerError(Exception):
+    pass
+
+
+class Synthesizer:
+    def __init__(self, nchannels, program):
+        self.channels = [Wave() for _ in range(nchannels)]
+        self.program = program 
+        # line_iter is None: "wait for segment selection" state
+        # otherwise: iterator on the current position in the segment
+        self.line_iter = None
+
+    def trigger(self, selection=None):
+        if selection is None:
+            if self.line_iter is None:
+                raise TriggerError
+        else:
+            if self.line_iter is not None:
+                raise TriggerError
+            self.line_iter = iter(self.program[selection])
+
+        r = [[] for _ in self.channels]
+        while True:
+            line = next(self.line_iter)
+
+            if line["dac_divider"] != 1:
+                raise NotImplementedError
+
+            for channel, channel_data in zip(self.channels,
+                                             line["channel_data"]):
+                if "bias" in channel_data:
+                    channel.bias.set_coefficients(channel_data["bias"])
+                if "dds" in channel_data:
+                    channel.dds.amplitude.set_coefficients(
+                        channel_data["dds"]["amplitude"])
+                    channel.dds.phase.set_coefficients(
+                        channel_data["dds"]["phase"])
+                    if channel_data["dds"]["clear"]:
+                        channel.dds.phase.clear()
+
+            for channel, rc in zip(self.channels, r):
+                for i in range(line["duration"]):
+                    rc.append(channel.next())
+
+            if line["wait_trigger"] and line["jump"]:
+                raise ValueError("Line cannot both jump and wait for trigger")
+            if line["wait_trigger"]:
+                return r
+            if line["jump"]:
+                self.line_iter = None
+                return r
+
+def main():
+    program = [
+        [
+            # segment 0
+            {
+                # line 0
+                "dac_divider": 1,
+                "duration": 100,
+                "channel_data": [
+                    {
+                        # channel 0
+                        "dds": {"amplitude": [0.0, 0.0, 0.01],
+                                "phase": [0.0, 0.0, 0.0005],
+                                "clear": False}
+                    }
+                ],
+                "wait_trigger": False,
+                "jump": False
+            },
+            {
+                # line 1
+                "dac_divider": 1,
+                "duration": 100,
+                "channel_data": [
+                    {
+                        # channel 0
+                        "dds": {"amplitude": [49.5, 1.0, -0.01],
+                                "phase": [0.0, 0.05, 0.0005],
+                                "clear": False}
+                    }
+                ],
+                "wait_trigger": False,
+                "jump": True
+            },
+        ],
+        [
+            # segment 1
+            {
+                # line 2
+                "dac_divider": 1,
+                "duration": 100,
+                "channel_data": [
+                    {
+                        # channel 0
+                        "dds": {"amplitude": [100.0, 0.0, -0.01],
+                                "phase": [0.0, 0.1, -0.0005],
+                                "clear": False}
+                    }
+                ],
+                "wait_trigger": False,
+                "jump": False
+            },
+            {
+                # line 3
+                "dac_divider": 1,
+                "duration": 100,
+                "channel_data": [
+                    {
+                        # channel 0
+                        "dds": {"amplitude": [50.5, -1.0, 0.01],
+                                "phase": [0.0, 100.05, -0.0005],
+                                "clear": False}
+                    }
+                ],
+                "wait_trigger": False,
+                "jump": True
+            }
+        ]
+    ]
+
     x = list(range(400))
-    w = Wave()
-
-    w.dds.amplitude.set_coefficients([0.0, 0.0, 0.01])
-    w.dds.phase.set_coefficients([0.0, 0.0, 0.0005])
-    y = [w.next() for i in range(100)]
-
-    w.dds.amplitude.set_coefficients([49.5, 1.0, -0.01])
-    y += [w.next() for i in range(100)]
-
-    w.dds.phase.set_coefficients([0.0, 0.1, -0.0005])
-    y += [w.next() for i in range(100)]
-
-    w.dds.amplitude.set_coefficients([50.5, -1.0, 0.01])
-    y += [w.next() for i in range(100)]
+    s = Synthesizer(1, program)
 
+    r = s.trigger(0)
+    y = r[0]
+    r = s.trigger(1)
+    y += r[0]
     cairoplot.scatter_plot("plot.png", [x, y])
+
+if __name__ == "__main__":
+    main()