Interesting topic you have here.
In the avant-garde genres, things are either truly innovative (for example, Mr. Bungle's Disco Volante or maudlin of the well's Bath), strange (Unexpect's In a Flesh Aquarium) or a blender of genres (Ram-Zet's Neutralized). These examples are just a few though. Though innovation can be
Beyond amazing, it can be the downfall of a band. This experimentation could go overboard and fail. Many people
SAW this with
Unexpect, saying that they used too many genres that it basically collapsed. Obviously a
Masterpiece can be created using the already existent materials, but when something new is introduced, it can become beautiful.
Let's take Devil Doll. To this day, no other band has sounded like them. Back in 1989, they released a dark classical/progressive rock metal type album that showed a huge amount of influences, but also a huge amount of innovative materials. Usage of the sprechsegang throughout the music, opera singing alongside it, full orchestra; it had all these new things.
There are many bands out there though that use a load of experimentation, but yet, they are absolutely horrible. Trying to implement another instrument that is not usually in metal can be dangerous.
To end my point, art is art regardless. Experimentation can be either the transcendental point of a band, or the downfall. A band could be just a rehash of an already processed sound, but it could be a
Rebirth of it. It depends on how it sounds in the end.
Last.fm: Mercenarion