On pages 46-49 it is rather unclear when is the best time to insert the USB Stick.
Those pages largely explain how to use the Internal Song Recorder, therefore we assume that a USB stick is not connected.
However, as noted in the first step:
* If a USB memory device is connected, press the FUNCTION 1 button (INT) to select the internal song recorder.
To convert a song to an audio file, you can probably insert the USB stick just prior to selecting this function, or leave the USB stick connected at all times, then press the FUNCTION 1 button after entering the Recorder, as explained in the note mentioned above.
I got it to work, proceeding thru 49.5.1 and then getting the Halt to insert the USB Stick.
I don't fully understand what you mean by 'Halt to insert the USB stick', however I just tried the following:
[Starting from the main playing screen (i.e. showing 'Concert Grand'), without connecting the USB stick]
1. Press the PLAY/STOP button
2. Press the FUNCTION 2 (EDIT) button
3. Move the cursor down to Conv.to Audio
4. Connect USB stick, wait for scanning
5. Press the FUNCTION 2 (ENTER) button
6. Select the Song/Part to Convert to MP3/WAV
7. Press the FUNCTION 2 (NEXT) button
8. Select the audio format (MP3/WAV)
9. Press the PLAY/STOP button, or a note on the keyboard
--> Conversion should start.
Then follow the normal USB Recorder save procedure.
I hope this helps.