I won't lie; chances are you already know the answer to "Non-mainstream, in genre names" and have no hope of finding the solution due to the complexity of the clue. If you can't figure it out on your own and are struggling with other clues, we've got you covered.

Now that we have given four clues, let's stop chatting and give the solution.

The word you are looking for is "ALT". It is a genre that is quite popular in rock and metal because of the diversity and size of what is considered alternative.

As for the clues, "Alt" is a shortened version of "Alternative," and if you add an "s" to the beginning of the clue, you get salt. Alt is seen as different from more conventional genres. Finally, "Alt" ends with the letter "t."