Low sound (note) from midi output keyboard in piano-roll

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Hi there,

I'm new to LMMS and just played around with it today.
I connected my keyboard to my pc with a MIDI to USB connector and I also want to playback the created songs on my keyboard.
So I added a preset, enabled midi input and output (same channel) and selected a sound on my keyboard. This worked fine, after opening the piano roll I was able to record some notes, and when playing back, the signal is sent back and played on my keyboard correctly. But when I select a note with my mouse in the piano-roll it immediatelly sends a signal to my keyboard and a very low bass-like sound (note) is played and never stops, it keeps playing (untill I turn off the keyboard).
I tried this a couple of times and it happens every time.

Does anyone know what is wrong? Maybe I have to change a configuration somewhere?

Thank you very much in advance

greetz,
Wouter
Welcome to LMMS forums.
Here is a good tutorial.
https://www.youtube.com/watch?v=uxZcunifT6w