How to Search a Roblox's Music using Proxy or httpservice?

I'll spoonfeed you. The simplest way is a quick GetAsync from http://rprxy.xyz.

Here is a basic function to get the ID from a search query.

local hs = game:GetService("HttpService")

function getSoundId(name)
    --format the query like a web browser url
    name = hs:UrlEncode(name)
    --get a massive string from this search
    local json = hs:GetAsync("https://rprxy.xyz/proxy/api/SearchMusic/"..name)
    --turn the string into a Lua table
    local tab = hs:JSONDecode(json)
    --this table is an array of dictionaries that describe assets
    --return the first item; the most relevant result; and it's id
    return (tab[1] or {}).AssetId
    --the operator prevents an error
end

Of course once you have the id you then simply plug it into a sound.