How to create a contextual filter to be used as the first character for a field? I create a view listing a field called authors the page path miSite.com/authors 

Then if I load this page I get the results:

Bach
Vivaldi
Vaccaro
Babbitt


This view page has the path: miSite.com/authors

I need to create a contextual filter to filter the result for the first character of the author field. I should work in this way:

1) If I load:

miSite.com/authors/b


I get the results:

Bach
Babbitt




2) If I load:

miSite.com/authors/v


I get the results:

Vivaldi
Vaccaro
You can create a contextual filter for the node title and configure it in "glossary mode". Provide a fixed value "a" and check the glossary mode settings at the bottom of the settings page.