First, many thanks for Florian for making this great app free. And congratulations to you for the boost in usability, performance and power : I had tried MP3Tag some years ago, and chose at that time to turn to MP3 Tag Studio. I'm glad I recently gave MP3Tag a try again, it's now my primary music files tage editor ! BTW, I guess the name should be changed : MP3Tag happens to work fine on my MPCs.
Now for my question :
I'd like to apply script commands this kind :
I'm sorry, but there's no concatenation operator at the moment. I think you can use $replace("%track%", "/", "-") - $validate("%title%", "_")
because it's very unlikely, that there are other special characters in your TRACK fields which needs validating.