Want to get technical?

YS282 describes it as "the Wizard's Death Curse."  So you have to be a wizard.  Does that mean you have to be on the White Council?  I'd rule probably not.  But I'd say that to have an effective death curse, you have to have full Evocation and full Thaumaturgy, and maybe the Sight too (which fills the template).  BCV Masters do not get a death curse unless they're also spellcasters of this calibre.

You do get a Death Curse if you're taken out though.  It's part of owning your death scene.  YS203 Sidebar. 

I'd say that an effective compel on aspects that would indicate that the dying NPC would not expect to die, would not have time to gather their thoughts, etc. would be enough to mitigate/eliminate a death curse.  Finally, I'd say death curses can only effect the characters that killed (specifically dealt a consequence to, or took out) the character, based on how they're portrayed in the books.

I'm quite impressed at the maturity of the responses.

The numbers and the Refresh investments are actually pretty important. That's why they're there. If they didn't matter, we'd get rid of them.

Arguably that's what FAE does.

I'm sure thing changed since the first playtest, but the way that DFAE handles characters of vastly different power levels was very interesting the first beta, dealing with degrees of success rather than odds of success.  I think the mechanic allows Harry and Butters (pre-all the things that are spoilery) to adventure together without one feeling useless.

Skills are the approaches, powers are...well an entirely different mechanic (and greatly simplified) that I don't know is what you're looking for.

If you want heavily customizable characters, DFRPG or FC are probably more to your tastes.  You're not going to be tweaking numbers the same way with any version of FAE.  Ultimately it's much more rules light, and designed for players who want that.  Given that you spend a good portion of time coming up with hoserules and homebrew, I don't know if it'll be your thing.

I would go with Alternate Magical Paradigm as well, though I usually grant my players that without paying a fate point, but only allow it if it fits the character concept. In this case, replacing discipline with performance seems reasonable enough. Maybe Conviction with (Stage) Presence as well.

The fiddle should probably be an item of power, yes. I would probably go with a music themed channeling, focus slots for defensive stuff, so you can buff your allies.
Unless the character has his own magic that the fiddle just helped bring to the front. In that case, you could drop the Item of Power and take the power yourself and then treat the fiddle as a focus item.

Marked by Power seems like a good fit as well, though not directly related to magic.

I really only make "Alternate Magical Paradigm" cost extra if someone tries to use it with things like fists, athletics, and endurance because that is definitely more powerful.  Having it with performance skills isn't any more powerful than the basic magic set, and may be noticeably weaker if mental enemies are common (like WCVs).

So basically call it Channeling but use Performance in place of discipline, Presence in place of conviction, and keep Lore where it is.  Easy enough.  I'd make the fiddle a focus item, personally, because I'd prefer to have the ability to use magic by singing, tapping out a beat, etc.  But if you're saying the power comes from the fiddle than make it an IoP.  To optimize refresh, add a point of Refinement on, or make it Evocation instead of Thaumaturgy.

Thematically, Air or Spirit would work well, or a different element like Music (work with your GM as to what it's limits should be).  If you go Evocation, Air, Spirit, and maybe Fire (since it's a bit infernal).

Thanks everyone. So I have been doing it right. As long as someone is willing/is able to take stress or can soak incoming stress by taking consequences, a character is still in the game. All his stress can be full, as long as he has consequences, he isn't taken out. It isn't until at least one point of stress "gets through" stress boxes and consequences that a character is taken out. Though a character can concede before that happens.

Choosing not to take a consequence and be taken out isn't a concession.

That's been one of my basic idea is computer/manga nerd all of suddenly loses direct access to technology but get magic... their for he tries to use magic like all the manga/computer he is read  or know.. The big problems i've ran into is is this how do i prevent him from breaking one of the laws and still learn the skills that way story wise. Even if he does brake the laws if he isn't apprentice he will still be looked at strangle by the council and all their traditions.

I do have another question that would effect my backstory is about the sight and soulgaze. When do wizards first get this abilities. is it when they fist unlock the powers or is after they ever reached certain level of magic ability....

...I'd have Luccio check up on him.  Tell him about the laws, and that she's watching him.  I'm inclined to think she'd be interested to see where his computer-code magic takes him.