confusion in variadic template

While exploring variadic templates, I found that recursive function could be with and without template but now my code is as below and I wondering why the add() is not called and neither the compiler throws any warning.

//why this one is not called   
void add(){
    std::cout << "[]";
}

template <typename T>
void add(T x){
    std::cout << x << "{}";
}

template <typename T, typename ...ARGS>
void add(T x, ARGS ...a){
    std::cout << x << ":";
    add(a...);
}   

int main()
{
  add(3.1, 3.4, "6.7", 4u, "7.54");
  return 0;
}

Also when I comment add(T x), the add() is called. I am confused.