What is the reason of filtering "_" and "~" symbols?

[kremnik]

Hi @rafaelvalle

In this line:

mellotron/text/__init__.py

Line 102 in d5362cc

return s in _symbol_to_id and s is not '_' and s is not '~'

you are filtering "_" and "~" symbols.
Also, one of the main advice to improve alignment map convergence is to add special symbols to start and end of every sentence. Usually these symbols are exactly "_" and "~" (ex: _What is your name?~). But you filter out exactly these symbols and do not add them anywhere in the code.

It is interesting, that you've included the "_" symbol here:

mellotron/text/symbols.py

Line 11 in d5362cc

_special = '_@©°½—₩€$'

but anyway filter it out next in sentence preprocessing.

So the questions are:

1. What is the reason of filtering out "_" and "~" symbols?
2. Why don't you use them as start and end symbols in sentences?