I tried building a metronome in JavaScript first. It seemed like the obvious choice - quick to prototype, tons of libraries, runs in the browser.
But the moment I tested it, the timing was off. Not by much, but enough to notice. The clicks drifted. The tempo wavered. It was unusable.
That is when I learned the hard truth: some problems need C++.
Not because it is better in every scenario. But because when you need precision, speed, and low-level control - JavaScript simply cannot deliver.
Here is what I learned building a metronome in C++, and the 10 core concepts you need to understand why it worked.
Why JavaScript Failed
JavaScript runs in a runtime environment that has no guaranteed timing precision. When you set a timer:
setInterval(() => playClick(), 500); // 120 BPM
You are not actually scheduling precise execution. You are asking the JavaScript engine to run your code "sometime around 500ms from now, if it is not busy."
The problem? JavaScript is single-threaded, and the event loop does not prioritize your metronome over:
- Garbage collection
- DOM updates
- Network requests
- Other timers
Real-world result: timing drift of 5-20ms per beat. Over 30 seconds, your metronome is noticeably off.
Even modern browsers throttle setInterval resolution to about 4-10ms to reduce CPU load, which further compounds drift.
This is not a bug. It is the design of the language. JavaScript was built for web interactivity, not real-time systems.
Why C++ Succeeds
C++ gives you low-level control over:
- Memory allocation
- Thread priority
- High-resolution system timers
- CPU scheduling
When you need a metronome click every 500ms, you can use high-resolution timers and dedicated threads to ensure it happens within a few microseconds or better, depending on OS scheduling granularity.
No garbage collector pauses. No event loop interference.
The First 10 C++ Concepts You Need
Here is what you need to learn to build something like this, and why each concept matters for performance-critical code.
1. Static Typing and Compilation
C++ is compiled, not interpreted. Your code is translated directly into machine instructions before it runs.
Why it matters for the metronome: No runtime type checking. No interpreter overhead. Every instruction is optimized for your specific CPU. The result is execution speed measured in nanoseconds, not milliseconds.
int tempo = 120; // Compiler knows this is an integer double interval = 60.0 / tempo; // Compiler optimizes this math
2. Manual Memory Management
In C++, you control when memory is allocated and freed. No garbage collector decides to pause your program mid-beat.
Why it matters: Garbage collection in JavaScript can pause execution for milliseconds at unpredictable times. In C++, you allocate what you need upfront and it stays allocated until you free it.
// Allocate memory once, use it throughout auto clickBuffer = std::make_unique<int[]>(sampleRate); // ... use clickBuffer.get() as needed ... // Automatically cleaned up when it goes out of scope
For a metronome, this means zero unexpected pauses. Modern C++ uses smart pointers like std::unique_ptr to manage memory safely and automatically.
3. Pointers and References
Pointers let you work directly with memory addresses. References let you pass data without copying it.
Why it matters: Audio buffers are large. Copying them every frame would kill performance. With pointers and references, you pass the memory location instead.
void fillAudioBuffer(float* buffer, int size) {
// Directly modify the buffer in place
for (int i = 0; i < size; i++) {
buffer[i] = generateSample(i);
}
}
4. The Standard Template Library (STL)
The STL provides data structures like vectors, queues, and maps that are heavily optimized.
Why it matters:
You get performance and convenience. Need a queue for buffering audio? std::queue is faster than anything you would write by hand.
#include <queue>
std::queue<float> audioQueue;
audioQueue.push(sample); // Fast, optimized, reliable
5. Multithreading with std::thread
You can create separate threads for time-critical tasks. Your metronome timing thread runs independently of everything else.
Why it matters: JavaScript is single-threaded. One slow operation blocks everything. In C++, your timing thread runs at high priority while other work happens in parallel.
#include <thread>
#include <chrono>
void timingLoop(double interval) {
while (running) {
playClick();
std::this_thread::sleep_for(std::chrono::duration<double>(interval));
}
}
std::thread timerThread(timingLoop, 0.5); // 500ms interval
While std::this_thread::sleep_for() is not real-time deterministic, it provides millisecond or better accuracy depending on the OS, far beyond JavaScript's timing guarantees.
6. High-Resolution Timers (std::chrono)
C++ provides nanosecond-precision timing through std::chrono.
Why it matters: You can measure time down to the nanosecond and schedule operations with far greater accuracy than JavaScript's millisecond timers.
#include <chrono>
auto start = std::chrono::high_resolution_clock::now();
// ... do work ...
auto end = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::microseconds>(end - start);
This level of precision is what makes the metronome rock-solid.
7. Classes and Object-Oriented Design
C++ classes let you encapsulate state and behavior. Your metronome can be a self-contained object.
Why it matters: Clean structure. The metronome object manages its own timing, audio generation, and state - keeping your code organized and maintainable.
class Metronome {
private:
int tempo;
bool running;
public:
void start() { running = true; }
void stop() { running = false; }
void setTempo(int bpm) { tempo = bpm; }
};
8. RAII (Resource Acquisition Is Initialization)
RAII is a C++ pattern where resources are tied to object lifetime. When an object is destroyed, its resources are automatically freed.
Why it matters: When your metronome object goes out of scope, everything cleans up automatically.
class AudioDevice {
public:
AudioDevice() { /* open device */ }
~AudioDevice() { /* close device */ } // Destructor guarantees cleanup
};
9. Header Files and Compilation Units
C++ separates declarations (headers) from implementations (source files). This enables modular code and faster compilation.
Why it matters: You can split your metronome into logical pieces: timing logic, audio generation, UI. Each compiles independently and links together at the end.
// metronome.h
class Metronome {
public:
void start();
void stop();
};
// metronome.cpp
#include "metronome.h"
void Metronome::start() { /* implementation */ }
10. Direct Hardware Access via Libraries
C++ libraries like RtAudio, PortAudio, and JUCE give you direct access to audio hardware with minimal latency.
Why it matters: You bypass layers of abstraction. Your code talks directly to the sound card, delivering audio with latency measured in milliseconds, not the 50-100ms delays common in browser audio.
#include <RtAudio.h>
RtAudio audio;
audio.openStream(/* params */);
audio.startStream(); // Direct hardware control
This is why professional audio software is written in C++.
Building the metronome finally made me understand why every professional audio plugin I have ever used, from reverbs to compressors to synthesizers, is written in C++, not JavaScript or Python. When you are processing audio in real time, you have roughly 10 milliseconds to process an entire buffer of samples before the next one arrives. Miss that deadline and you get clicks, pops, and dropouts.
In real-time audio systems, callbacks and non-blocking I/O replace traditional loops to avoid timing jitter. Your audio processing function is called by the system at precise intervals, and you must finish before the next buffer arrives.
JavaScript and Python simply cannot guarantee that performance. Their garbage collectors, interpreters, and runtime overhead make them unsuitable for real-time audio. C++ is not just preferred in professional audio, it is the only practical choice.
The Real Difference: Deterministic Performance
JavaScript gives you convenience. C++ gives you control.
For most applications, JavaScript is fine. But when you need:
- Precise timing (games, audio, video)
- Low latency (real-time communication, musical instruments)
- Predictable performance (embedded systems, robotics)
- Maximum speed (simulations, data processing)
C++ is often the only option.
When to Use Each
Both belong in a developer's toolkit. JavaScript gets you results quickly; C++ keeps them rock-solid.
Use JavaScript when:
- Building web interfaces
- Prototyping quickly
- Working with APIs and services
- You need "good enough" performance
Use C++ when:
- Timing precision is critical
- You need maximum performance
- You are working close to hardware
- Consistency matters more than convenience
Getting Started with C++
If you want to try C++ yourself:
- Install a compiler (GCC, Clang, or MSVC)
- Get an IDE (VS Code with C++ extensions, CLion, or Visual Studio)
- Start with simple programs - no need to build a metronome on day one
- Learn the syntax, then gradually add complexity
C++ has a steeper learning curve than JavaScript, but the payoff is worth it when you need it.
Final Thought
I do not write everything in C++. Most of my work is still in Python and JavaScript because they are faster to write and easier to maintain.
But when I need something that absolutely must work correctly, every single time, with zero drift, C++ is the only answer.
That is vibecoding. Build with the right tool for the job.