USB-MIDI Library.

I am trying to run a test program that uses the USB-MIDI Library.
When I try and load the sketch I get the following error
#error MIDIUSB can only be used with an USB MCU.

On reading up about the error I assumed I had to install HoodLoader2.
I upgraded the firmware as per the instructions and my Led blinker fast.
Unfortunately there was no instructions on how to check working on a Mac.
Or how to use.

If I go into "About this mac" and then system setting and look under USB I get
HoodLoader2 Uno:

Product ID: 0x0043
Vendor ID: 0x2341
Version: 2.05
Speed: Up to 12 Mb/sec
Manufacturer: NicoHood
Location ID: 0x14100000 / 10
Current Available (mA): 1000
Current Required (mA): 100
Extra Operating Current (mA): 0

Which makes me think I have the firmware installed okay. But no idea of how to use

I think it means you need an Arduino with a 32u4 processor like the Leonardo or the Micro. The ATmega328p processor on the Arduino UNO does not have USB hardware built in.

So HoodLoader 2 is not an option in your view.

You’ll have to use a ‘normal’ serial port MIDI library. Then upload the sketch and finally flash the HoodLoader firmware onto the ATmega 16U2.

The USB-MIDI library only works on Arduino’s that have a main processor with a USB interface. The Uno has a second microprocessor for USB communication.

The main processor, the ATmega 328P, has a Serial connection on pins 0 and 1 connected to the serial port of the second processor, the ATmega 16U2. The 16U2 converts the serial connection to a USB connection and vice versa.

The default firmware that runs on the 16U2 is USB-to-serial firmware that behaves like a serial (COM) port. By removing this default firmware, and installing custom MIDI firmware, you can convert the serial connection to MIDI over USB. The computer will then see the Arduino as a MIDI device instead of a serial port.