diff --git a/src/tangara/audio/audio_events.hpp b/src/tangara/audio/audio_events.hpp
index f7eaba67..55095d85 100644
--- a/src/tangara/audio/audio_events.hpp
+++ b/src/tangara/audio/audio_events.hpp
@@ -86,6 +86,10 @@ struct SetTrack : tinyfsm::Event {
   std::optional<uint32_t> seek_to_second;
 };
 
+struct PlaySineWave : tinyfsm::Event {
+  uint32_t frequency;
+};
+
 struct TogglePlayPause : tinyfsm::Event {
   std::optional<bool> set_to;
 };
diff --git a/src/tangara/audio/audio_fsm.cpp b/src/tangara/audio/audio_fsm.cpp
index 71f41938..fb186acc 100644
--- a/src/tangara/audio/audio_fsm.cpp
+++ b/src/tangara/audio/audio_fsm.cpp
@@ -11,6 +11,8 @@
 #include <memory>
 #include <variant>
 
+#include "audio/audio_source.hpp"
+#include "audio/sine_source.hpp"
 #include "cppbor.h"
 #include "cppbor_parse.h"
 #include "esp_heap_caps.h"
@@ -146,6 +148,17 @@ void AudioState::react(const SetTrack& ev) {
   });
 }
 
+void AudioState::react(const PlaySineWave& ev) {
+  auto tags = std::make_shared<database::TrackTags>();
+
+  std::stringstream title;
+  title << ev.frequency << "Hz Sine Wave";
+  tags->title(title.str());
+
+  sDecoder->open(std::make_shared<TaggedStream>(
+      tags, std::make_unique<SineSource>(ev.frequency), title.str()));
+}
+
 void AudioState::react(const TogglePlayPause& ev) {
   sIsPaused = !ev.set_to.value_or(sIsPaused);
   if (!sIsPaused && is_in_state<states::Standby>() &&
diff --git a/src/tangara/audio/audio_fsm.hpp b/src/tangara/audio/audio_fsm.hpp
index 03aaddcb..82f0a3ad 100644
--- a/src/tangara/audio/audio_fsm.hpp
+++ b/src/tangara/audio/audio_fsm.hpp
@@ -44,6 +44,7 @@ class AudioState : public tinyfsm::Fsm<AudioState> {
   void react(const tinyfsm::Event& ev) {}
 
   void react(const QueueUpdate&);
+  void react(const PlaySineWave&);
   void react(const SetTrack&);
   void react(const TogglePlayPause&);
 
diff --git a/src/tangara/audio/sine_source.cpp b/src/tangara/audio/sine_source.cpp
new file mode 100644
index 00000000..9a5a12b9
--- /dev/null
+++ b/src/tangara/audio/sine_source.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "audio/sine_source.hpp"
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <numbers>
+
+#include "esp_log.h"
+
+#include "audio/audio_source.hpp"
+#include "codec.hpp"
+#include "drivers/spi.hpp"
+#include "sample.hpp"
+#include "system_fsm/system_events.hpp"
+#include "types.hpp"
+
+namespace audio {
+
+[[maybe_unused]] static constexpr char kTag[] = "sine_src";
+
+SineSource::SineSource(uint32_t freq)
+    : IStream(codecs::StreamType::kNative),
+      step_(0),
+      increment_((2.0 * std::numbers::pi) / (48000.0 / freq)) {}
+
+auto SineSource::Read(std::span<std::byte> dest_bytes) -> ssize_t {
+  std::span<sample::Sample> dest{
+      reinterpret_cast<sample::Sample*>(dest_bytes.data()),
+      dest_bytes.size_bytes() / sizeof(sample::Sample)};
+
+  for (size_t i = 0; i < dest.size(); i++) {
+    dest[i] = std::numeric_limits<sample::Sample>::max() *
+              std::sin(step_ += increment_);
+  }
+
+  return dest.size_bytes();
+}
+
+auto SineSource::CanSeek() -> bool {
+  return false;
+}
+
+auto SineSource::SeekTo(int64_t destination, SeekFrom from) -> void {}
+
+auto SineSource::CurrentPosition() -> int64_t {
+  return 0;
+}
+
+auto SineSource::Size() -> std::optional<int64_t> {
+  return {};
+}
+
+}  // namespace audio
diff --git a/src/tangara/audio/sine_source.hpp b/src/tangara/audio/sine_source.hpp
new file mode 100644
index 00000000..6d514479
--- /dev/null
+++ b/src/tangara/audio/sine_source.hpp
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2023 jacqueline <me@jacqueline.id.au>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+
+#include "codec.hpp"
+#include "ff.h"
+
+#include "audio/audio_source.hpp"
+
+namespace audio {
+
+/*
+ * Generates an infinitely long sine wave of a specified frequency.
+ */
+class SineSource : public codecs::IStream {
+ public:
+  SineSource(uint32_t frequency);
+
+  auto Read(std::span<std::byte> dest) -> ssize_t override;
+
+  auto CanSeek() -> bool override;
+
+  auto SeekTo(int64_t destination, SeekFrom from) -> void override;
+
+  auto CurrentPosition() -> int64_t override;
+
+  auto Size() -> std::optional<int64_t> override;
+
+  SineSource(const SineSource&) = delete;
+  SineSource& operator=(const SineSource&) = delete;
+
+ private:
+  double step_;
+  double increment_;
+};
+
+}  // namespace audio