Make sure to use ASIO drivers. You can configure that in the program settings of Music Maker. Switch the driver model to ASIO and configure the Magix Low Latency option as generic ASIO driver, if your sound hardware doesn't provide its own ASIO drivers. However, ultimately, this might just be a technical limitation of your sound hardware. (It might just operate in half-duplex mode.) Make sure to use a dedicated sound hardware that allows for full-duplex operation.