DonM and George. Thanks for the tip. It works as expected, but the problem stays the same. After the voice change I get a short stop in sounding, working with the OTS or without. It is true that this is not the case with every voice.

Please try this on your keyboards: Select Ballad: 8BeatModern style and switch the OTS link on. Play the right hand sound and keep the voice sounding while pressing another variation. Do you hear the interrupt? If not It is something wrong with my keyboard.

Thank you very much for your response.
Marko