diff --git a/examples/audio.cpp b/examples/audio.cpp
index 90a48c1a..4da79e78 100644
--- a/examples/audio.cpp
+++ b/examples/audio.cpp
@@ -16,6 +16,7 @@
 #include <psemek/audio/combine/duplicate.hpp>
 #include <psemek/audio/combine/stereo.hpp>
 #include <psemek/audio/combine/mixer.hpp>
+#include <psemek/audio/midi.hpp>
 #include <psemek/app/app.hpp>
 #include <psemek/app/main.hpp>
 #include <psemek/gfx/painter.hpp>
@@ -101,7 +102,7 @@ struct audio_app
 			int midi = key_to_midi.at(key);
 			if (!channels_.contains(midi))
 			{
-				auto tone = audio::karplus_strong(440.f * std::pow(2.f, (midi - 69) / 12.f));
+				auto tone = audio::karplus_strong(audio::midi_frequency(midi));
 				tone = audio::distortion(std::move(tone), 4.f);
 				channels_[midi] = mixer_->add(audio::fade_in(tone, 0.005f));
 			}
diff --git a/libs/audio/include/psemek/audio/midi.hpp b/libs/audio/include/psemek/audio/midi.hpp
new file mode 100644
index 00000000..f953bf26
--- /dev/null
+++ b/libs/audio/include/psemek/audio/midi.hpp
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <cmath>
+
+namespace psemek::audio
+{
+
+	inline float midi_frequency(float note)
+	{
+		return 440.f * std::pow(2.f, (note - 69.f) / 12.f);
+	}
+
+}