Setting up LDAP is fairly straight-forward, assuming your LDAP server is already configured properly (a topic outside the scope of this document–a good tutorial on authentication with LDAP can be found at http://times.usefulinc.com/2005/09/25-ldap).
To configure LDAP, add the following to your /config/ampache.cfg.php and fill in all of the ldap_* configuration values.
auth_methods = "ldap"
The above example does not include MySQL authentication support. Ampache can have multiple authentication methods at the same time. It will try them in the order they are listed until a match is found. If you would like it to try ldap first, and then fall back on mysql simply set auth_methods as follows.
auth_methods = "ldap,mysql"