Viftool

You can use this tool as the original but it is updated to use the file names
from the TomTom 920T custom voice recordings.
Also these files need to be converted to .ogg files before joined by this
script. Also some of the files are NOT produced by the 920T, but the script will
show what's missing, these have to be added manually.

With this script you can separate chk files to have all the ogg files and then
editing those audio files you can put it together again.
 
Convert the wav files to ogg files with 22050 Hz mono and variable bitrate of 
5% (oggenc -b 40 voice.wav), the dataXX.chk file package size should be around
1Mbyte, higher might not be accepted by the TomTom software.

Examples: 

Join the files:
python viftool.py join 75 name data75.chk

Split a package:
python viftool.py split data75.chk