Batch process

For example:

A1-Mike Mango - Believe
A2_Groove Riders - Love
B1 Dataworx - Banger
B2_-_Tom Hades - Connect
01.Fader - Move
02-Moonwalker - Day Two

I remove digit with this:
$trimLeft(%filename%,'0123456789).- ')

How to remove A1,A2,B1,B2 from tunes?

you can remove the first characters with a number of functions, e.g.
$regexp(%fieldname%,'^...(.*)',$1)
but as you do not have a common pattern
(sometimes just 3 characters, sometimes 5 like in "B2_-_Tom Hades - Connect") you will be left with some remainders.

Why don't you import the data into tag fields first so that the amorphous string become more structured data and then write a new filename with data from the tag fields?

thanks for answer. this is .wav files and all fields are empty, only _FILENAME.
Will try. thanks.

WAV files can also have tags. MP3tag has that feature since a couple of versions ago.

Check it out on a test tagfield, ... probably you can do it this way:

Action "Format value" ... or ... Convert "Tag-Tag"

FN_TEST <== $regexp(%filename%,'^[AB]?\d+[-. ]+',)

DD.20180124.1556.CET