This was deleted shortly before the voice recorder failed. There is an 'erase' button which is quite prominent and it will format the device if depressed.

I see that as a problem..

Erasing

1 Select the file you want to erase.
2 While the recorder is during stop mode, press the ERASE button.

• File number and [NO] will flash on the display.

3 Press the 0 button to select [yES].

4 Press the `OK button.

• Erasing begins and [ERASE] flashes on the display.

Erasing all files:

1 While the recorder is during stop mode, press the ERASE button.

2 Press the ERASE button again.

• [ALL] and [NO] will flash on the display.

3 Press the 0 button to select [yES].

4 Press the `OK button.

• Erasing begins and [ERASE] flashes on the display.

• If an action is not selected within 8 seconds, the recorder will return to stop mode.

• It may take over 10 seconds to complete processing. Never remove batteries during this time because data may be corrupted. In addition, carefully check the remaining battery level in order to ensure that the battery will not run out while processing.

He is the primary author of the Speex codec and one of the main authors of the Opus codec, both of which provide a free alternative to patented, proprietary audio codecs.

I wonder if it might be worth contacting this person:
https://people.xiph.org/~jm/


Speex is based on CELF.