# Routing MIDI Messages

> Original: [Routing MIDI messages](https://tttapa.github.io/Control-Surface/Doxygen/d3/df7/midi-tutorial.html)

## Default routing

`Control_Surface.begin()` automatically connects the default MIDI interface to all output and input elements. For single-interface projects, no manual routing is needed.

## MIDI Pipes

Pipes connect sources to sinks. Use shift operators:

```cpp pico
MIDI_PipeFactory<2> pipes;
midi1 >> pipes >> midi2;  // midi1 sends to midi2
midi2 >> pipes >> midi1;  // midi2 sends to midi1
```

## Bidirectional pipes

```cpp pico
BidirectionalMIDI_PipeFactory<1> bpipes;
midi1 | bpipes | midi2;
```

## Custom filtering

Subclass `MIDI_Pipe` and override `mapForwardMIDI`:

```cpp pico
struct ChannelFilter : MIDI_Pipe {
    Channel allowed;
    ChannelFilter(Channel ch) : allowed(ch) {}

    void mapForwardMIDI(ChannelMessage msg) override {
        if (msg.getChannel() == allowed)
            sourceMIDItoSink(msg);
    }
    void mapForwardMIDI(SysExMessage msg) override {
        sourceMIDItoSink(msg);
    }
    void mapForwardMIDI(SysCommonMessage msg) override {
        sourceMIDItoSink(msg);
    }
    void mapForwardMIDI(RealTimeMessage msg) override {
        sourceMIDItoSink(msg);
    }
};

ChannelFilter ch1Only {Channel_1};
// midi >> ch1Only >> otherMidi;
```

## Multi-interface example

```cpp pico
#include "pico/stdlib.h"
#include "pico/cyw43_arch.h"
#include <cs_midi.h>

using namespace cs;

BluetoothMIDI_Interface ble;
USBMIDI_Interface usb;

BidirectionalMIDI_PipeFactory<1> pipes;

int main() {
    stdio_init_all();
    if (cyw43_arch_init()) return 1;
    ble | pipes | usb;
    Control_Surface.begin();
    while (true) {
        Control_Surface.loop();
        sleep_ms(1);
    }
}
```