Midi OUT --> Serial.write not working??

Hi,

i'm new in Arduino-programming and my first project is a midi controller which has to control a drum machine.
Various Piezo's are connected to the AnalogInputs and a MIDI-Signal is to be sent by a MIDI Output to a Windows-XP system (which drives the Drum machine).

Guideline for my project is this project:

For first startup i have limited the schematic to one piezo and a simpler code.

The Electronic schematic:

A piezo is connected to Analog Input 0.
When the piezo is hit, the velocity is read by piezoVal=AnalogRead(0) and then sent by

Serial.Write(0x90); // Midi-On command
Serial.Write(38); // Fixed Midi-Note
Serial.Write(piezoVal);
Delay(200);
Serial.Write(0x80); // Midi-On command
Serial.Write(38); // Fixed Midi-Note
Serial.Write(0);

The Midi-Out is connected as follows:
Middle Pin connected to ground
Pin 2 is connected to TX0
Pin 5 is connected to 220kOhm Resistor and then to 5V-Pin

What works:
If i hit the Piezo, the signal is correctly detected (and shown in the Serial Monitor).
Every time i hit the Piezo the RX LED lights up (shouldn't it be the TX LED??)

What doesn't work:
No Midi Signal is arriving at the Window's Midi In-Port.

What i have tested already:

Connected a Roland Drum Modul to the Windows Midi-IN
--> Success --> Means MIDI-In and MIDI cable correctly working

Changed MiDI-PCB-JACK
--> Still no Signal

Tried to use TX1 Port and changed sketch to

void setup() {

Serial1.begin(31250); // MIDI Baud rate

}

void loop() {
Serial1.write[...]
}

Is there any way to check if my Serial Port TX0 is working?

Any help is appreciated.

Best regards

Daniel

basementmedia:
The Midi-Out is connected as follows:
Middle Pin connected to ground
Pin 2 is connected to TX0
Pin 5 is connected to 220kOhm Resistor and then to 5V-Pin

That doesn't sound right. Take a look at the official MIDI specification schematics:
https://tttapa.github.io/Arduino/MIDI/Chap02-MIDI-Hardware.html

Are you trying to do MIDI over USB? What is MiDI-PCB-JACK?

Pieter