diff --git a/README.md b/README.md
index 6abe15e..793c8f5 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,12 @@ cmake ..
 make tone-generator
 ```
 
+## Rules of SELCAL Codes
+- Letters must not be duplicated across the whole code
+- Within each of the two groups, letters must be sorted alphabetically
+- AB-CD and CD-AB are valid.
+- AA-CD and BA-CD are not valid.
+
 ## Build with system packages?
 Requires the following packages (debian)
 
diff --git a/python/.gitignore b/python/.gitignore
new file mode 100644
index 0000000..697e56f
--- /dev/null
+++ b/python/.gitignore
@@ -0,0 +1 @@
+*.wav
\ No newline at end of file
diff --git a/python/requirements.txt b/python/requirements.txt
new file mode 100644
index 0000000..b4854e1
--- /dev/null
+++ b/python/requirements.txt
@@ -0,0 +1 @@
+tones==1.2.0
diff --git a/python/tonegen.py b/python/tonegen.py
new file mode 100755
index 0000000..2208b0a
--- /dev/null
+++ b/python/tonegen.py
@@ -0,0 +1,36 @@
+#! /usr/bin/env python3
+
+from tones import SINE_WAVE, SAWTOOTH_WAVE, SQUARE_WAVE
+from tones.mixer import Mixer
+import csv
+import sys
+
+GROUP_DURATION = 1.0
+SILENCE_DURATION = 0.2
+CHANNELS = 2
+
+tones = {}
+with open('tones.csv', newline='') as csvfile:
+    reader = csv.DictReader(csvfile)
+    for row in reader:
+        tones[row['designator']] = float(row['frequency'])
+
+code = sys.argv[1]
+print(f"Generating tone for SELCAL {code}")
+
+# Create mixer, set sample rate and amplitude
+mixer = Mixer(44100, 1)
+for i in range(CHANNELS):
+    mixer.create_track(i, SQUARE_WAVE)
+
+groups = code.split("-")
+for groupindex,group in enumerate(groups):
+    for channel,tone in enumerate(group):
+        mixer.add_tone(channel, frequency=tones[tone], duration=GROUP_DURATION)
+
+    if groupindex != len(groups) - 1:
+        for i in range(CHANNELS):
+            mixer.add_silence(i, duration=SILENCE_DURATION)
+
+# Mix all tracks into a single list of samples and write to .wav file
+mixer.write_wav(f'{code}.wav')
diff --git a/python/tones.csv b/python/tones.csv
new file mode 100644
index 0000000..d5f68a7
--- /dev/null
+++ b/python/tones.csv
@@ -0,0 +1,33 @@
+designator,frequency
+1,680.0
+2,754.2
+3,836.6
+4,927.9
+5,1029.2
+6,1141.6
+7,1266.2
+8,1404.4
+9,1557.8
+A,312.6
+B,346.7
+C,384.6
+D,426.6
+E,473.2
+F,524.8
+G,582.1
+H,645.7
+J,716.1
+K,794.3
+L,881.0
+M,977.2
+P,1083.9
+Q,1202.3
+R,1333.5
+S,1479.1
+T,329.2
+U,365.2
+V,405.0
+W,449.3
+X,498.3
+Y,552.7
+Z,613.1
\ No newline at end of file