Introduction

The deepnote library provides a C++14 header-only implementation of a synthesizer voice inspired by the iconic THX Deep Note sound effect.

Key Features

Header-only library: No compilation required, just include and use
Real-time performance: Optimized for audio applications
Multiple oscillators: Support for up to 16 detuned oscillators per voice
Bezier curve shaping: Smooth, controllable frequency transitions
Strong typing: Type-safe API prevents common audio programming errors
Comprehensive testing: Full test coverage with doctest framework

Quick Start

#include "voice/deepnotevoice.hpp"
 
using namespace deepnote;
 
// Create and initialize a voice
DeepnoteVoice voice;
init_voice(voice, 3, nt::OscillatorFrequency(200.0f), 
          nt::SampleRate(48000.0f), nt::OscillatorFrequency(0.5f));
 
// Set target frequency for animation
voice.set_target_frequency(nt::OscillatorFrequency(8000.0f));
 
// Process audio samples
for (size_t i = 0; i < num_samples; ++i) {
    auto output = process_voice(voice, nt::AnimationMultiplier(1.0f),
                               nt::ControlPoint1(0.25f), nt::ControlPoint2(0.75f));
    audio_buffer[i] = output.get();
}

Architecture Overview

The library is organized into several key components:

DeepnoteVoice: Main voice class containing oscillators and state machine
State Machine: Manages transitions between PENDING → IN_TRANSIT → AT_TARGET
LFO Animation: Controls the speed and timing of frequency transitions
Bezier Shaping: Provides non-linear curve shapes for natural-sounding animations
Strong Types: Type-safe wrappers around float values (frequencies, rates, etc.)

Performance Characteristics

CPU Usage: ~50 + (20 × num_oscillators) cycles per sample
Memory Usage: ~2KB per voice (fixed allocation)
Real-time Safe: No dynamic allocation in audio processing paths
Scalable: Support for 1-16 oscillators depending on performance requirements

Examples

See the docs/examples/ directory for complete usage examples:

basic_usage.cpp - Simple Deep Note generation
vcvrack_integration.cpp - VCV Rack module integration
daisy_seed_integration.cpp - Embedded hardware usage

Testing

The library includes comprehensive unit tests using the doctest framework:

cd test
mkdir build && cd build
cmake .. && make
./bin/tests

License

This project is licensed under the MIT License - see LICENSE.txt for details.

Acknowledgments

Inspired by the THX Deep Note sound effect
Built on the DaisySP digital signal processing library
Uses doctest for unit testing framework