Alright when/if this happens I want to do vocals

I don't now how someone can get scared when listening music, but maybe you should try Symphonic Black Metal.

Hardly the ideal choice. You'd be better off dropping the symphonic elements in my opinion.

"Scary" music can be achieved in all genres. It's about the general feeling of the song, the dynamics, the tone, etc. Check out the band Atomic Rooster. They came out in 1972 (I think, don't quote me on that), and they sound pretty scary.

Why? Plenty of symphonies have played creepy-sounding music. It's usually easier in a chamber group, though. Minimalism usually sounds off-putting and generally weird.

one guitar rif ,one blast beat on drums and screaming and growling that's the best thing

I find atmosphere to be a much better tool in making music scary than creepy synths.

So, synthesizers can't have atmosphere? If you're really lucky, you might know some people who actually play violin, viola, cello, double-bass, etc. I saw some doom band a while back that actually had a cellist on stage, it was wicked.

Black metal becomes symphonic when you add synthesisers?

Listen to the whole Death - Pierce Me album by Silencer. That album especially the vocals are both terrifying and laughable at first listen.

maybe focusing on song production it self like adding a lot of stereo elements >>>this would help making music scary
and with some mysterious piano like Halloween (the movie)

I just experimented with some guitar effects, and I noticed that ghost bending with lots of reverb (I mean lots) sounds quite scary, if you can call it that. Playing that with some mysterious eastern sounding scale and occassionally sliding your finger down the neck for a special effect will help make it very strange and, well, scary I guess.

For the most part, use harmonic minor scales with some tritones thrown in. Also, go for a sound that is very strange and atmospheric. Use a low quality recording. Reverb with tremolo picking works well.