diff --git a/transcoder/audio.py b/transcoder/audio.py
index ea3f7f9..04b8084 100644
--- a/transcoder/audio.py
+++ b/transcoder/audio.py
@@ -1,3 +1,5 @@
+"""Encodes input audio stream into sequence of speaker duty cycle counts."""
+
 from typing import Iterator
 
 import audioread
diff --git a/transcoder/edit_distance.py b/transcoder/edit_distance.py
index 8b27c66..9794fc9 100644
--- a/transcoder/edit_distance.py
+++ b/transcoder/edit_distance.py
@@ -1,3 +1,5 @@
+"""Computes visual differences between screen image data."""
+
 import functools
 
 import numpy as np
diff --git a/transcoder/opcodes.py b/transcoder/opcodes.py
index f4db11a..c236332 100644
--- a/transcoder/opcodes.py
+++ b/transcoder/opcodes.py
@@ -1,3 +1,5 @@
+"""Opcodes representing discrete operations of video player."""
+
 import enum
 from typing import Iterator, Tuple
 
diff --git a/transcoder/opcodes_test.py b/transcoder/opcodes_test.py
index beb0199..4121950 100644
--- a/transcoder/opcodes_test.py
+++ b/transcoder/opcodes_test.py
@@ -1,3 +1,5 @@
+"""Tests for the opcodes module."""
+
 import unittest
 
 import opcodes
diff --git a/transcoder/symbol_table.py b/transcoder/symbol_table.py
index 8841899..097cd85 100644
--- a/transcoder/symbol_table.py
+++ b/transcoder/symbol_table.py
@@ -1,3 +1,5 @@
+"""Parses the cc65 .dbg output to extract symbol addresses."""
+
 from typing import Dict
 
 
diff --git a/transcoder/symbol_table_test.py b/transcoder/symbol_table_test.py
index 965b36c..111ebeb 100644
--- a/transcoder/symbol_table_test.py
+++ b/transcoder/symbol_table_test.py
@@ -1,3 +1,5 @@
+"""Tests for the symbol_table module."""
+
 import io
 import unittest
 
diff --git a/transcoder/video.py b/transcoder/video.py
index 3162937..534e2a8 100644
--- a/transcoder/video.py
+++ b/transcoder/video.py
@@ -1,3 +1,5 @@
+"""Encode a sequence of images as an optimized stream of screen changes."""
+
 import heapq
 import os
 import queue
diff --git a/transcoder/video_test.py b/transcoder/video_test.py
index 2bd4eb2..30e6db2 100644
--- a/transcoder/video_test.py
+++ b/transcoder/video_test.py
@@ -1,3 +1,5 @@
+"""Tests for the video module."""
+
 import unittest
 
 import video