LED to Midi

Hello,
i want to build a simple Arduino Project. I have a simple Metronom for guitars which has an audio output but also a blinking LED and convert the blinking LED to a Midi-Tempo signal.

I know there are machines who can do this directly, but i want to keep it simple and just use the voltage of that LED. as with this the method can be used across a lot of different devices which indicate tempo via an LED.

I have an arduino Duo and a MIDI-Shield ordered. I see there is a project which does the same thing but uses a button instead of the LED. GitHub - DieterVDW/arduino-midi-clock: Arduino Master MIDI clock implementation with tap tempo

so my question is (as i am not a hardware guy) can i use the LED voltage in the same way as a closed button. Or do i need somethign like an optocoupler in parallel with the LED to achieve the same thing. is the optocoupler "fast" enough?

Or do i need somethign like an optocoupler in parallel with the LED to achieve the same thing. is the optocoupler "fast" enough?

Yes and yes.

The opto-coupler will need a separate current-limiting resistor to the LED - otherwise it'll take
all the current and the LED will stop working.