Electronic keyboard musical instrument and method of generating musical sound

An electronic keyboard musical instrument comprising:

• a keyboard including a first key and a plurality of low-register keys on a low register side;
• a processor;
• and
• a sound source,
• wherein
• the sound source is configured to, in response to detection of key-pressing of the first key in damper-off detection by the processor, execute processing of:
• inputting first excitation signal data corresponding to the first key to a first channel which corresponds to the first key,
• inputting first channel output data which is output from the first channel in response to input of the first excitation signal data to each of low-register channels corresponding to the respective low-register keys, and
• outputting musical sound data which is generated based on respective pieces of low-register channel output data which is output from the respective low-register channels in response to the input of the first channel output data and the first channel output data output from the first channel, as musical sound data corresponding to the first key.