Accessing multiple USB MIDI ports

[GModal]

I'm working with an ESP32-S3 board, and my project successfully connects to a BLE MIDI peripheral, and sends MIDI data to a USB-OTG MIDI port, plugged into my PC (Ubuntu / Pipewire & JACK). It works very well, currently (thanks everyone!).

And Creating multiple USB MIDI ports in the sketch seems straight-forward:

Adafruit_USBD_MIDI usb_midi(2);

// Create a new instance of the Arduino MIDI Library,
MIDI_CREATE_INSTANCE(Adafruit_USBD_MIDI, usb_midi, MIDI);

void setup() {
    usb_midi.setCableName(1, "BLE-1");
    usb_midi.setCableName(2, "BLE-2");
    MIDI.begin();
    Serial.begin(115200);

    .... snip .....
}

// send MIDI from BLE input buffer:
void sendMIDI() {
    MIDI.send(midi::MidiType (bbuf[2] & 0xF0), bbuf[3], bbuf[4], (bbuf[2] & 0x0F) + 1);
}

The two USB MIDI ports appear on my PC, but I'm having difficulty sending MIDI data to the second port. I'm clearly misunderstanding how to access the second stream defined in usb_midi .