What is the head voice you often hear about? Is it a register created in your head?
Well, that question might seem silly – head voice, or all registers, for that matter, are created directly at your vocal folds. It is a function where the folds vibrate mostly only by their edges and this creates a feeling of resonance high in the head, a flute-like sensation. It is a legitimate use of the voice that especially female singers absolutely need.  But so do male singers, as well; only it sounds a little different and has a lot to do with their ability to learn the mix, enabling them to reach their higher range.
Many female beginning singers think they don´t have high notes. Their false assumption is often based on their having sung mostly pop and rock with a rather heavy approach. It suits that kind of music very well but might limit the range unnecessarily. Voice teachers even refer to this way of singing as heavy mechanism. Singers need to get to know their head voices, too, to be able to mix these register sensations and acquire a wide and flexible range. It really has nothing to do with the musical style or genre, rather it is an important part of any singer´s techique. Classical singers absolutely need it, whether they are sopranos, mezzos or contraltos.
So, how can you find your head voice?
Try these tips:
Pretend to be a cuckoo. Cuckoo, cuckoo!  or ooh-ooh! Lightly let out two highish sounds of any pitch, imitating that famous bird. How does it feel? Light and easy, I  hope? Or imitate a puppy: hmee, hmee, very lightly and sweetly. Don´t think about singing, just let those sounds come as if you were a child playing with your voice. Don´t be afraid if these sounds seem separate from the rest of your voice at first. When you get the idea, experiment doing slides from the lower part of your voice to this newfound higher range. Play the siren of an ambulance! Play, have fun! This is a primal sound that will bring your natural vocal function into life.
After doings these funny exercises you are going to notice that your voice gets more flexible and higher notes will come easier. Don´t be afraid you sound too classical!! If you DO want to sound classical, this is the way to develop. On the other hand, if you find classical singing unnatural (well, it kindof  is, because it is an art, after all) – still keep doing these slides for the sake of flexibility. There is a way of integrating your non-classical sound to this high mix. More about that later.
A word of warning: if these exercices don´t work – if your voice cracks a lot, if you must push air and it hurts, it could be a sign of your vocal folds being swollen, due to an overworked state, vocal abuse, sickness like a common cold,  laryngeal reflux, asthma or the like. Then just let your voice rest and if this condition doesn´t go away in 2 weeks, see a doctor.  However, a little cracking or breaking while ascending the scale on a slide doesn´t necessarily mean anything serious. We do have breaks or areas in our voices where the register changes take place and it is quite natural in the beginning for the voice to feel uneven, insecure or to crack sometimes on certain pitches. It´s like driving a car with manual gears, you can´t change gears really smoothly at first. This will go away with practice. Find part of  your head voice feeling already at the lower part of your range; then changing registers will start to happen more evenly. Or try practicing from above first, especially on an oo-vowel (Italian u)
The clear head voice is in fact a sure sign of vocal well being, healthy vocal folds. That´s why these exercises are so telling and important. But now, let your neighbors enjoy your slides and sirens! Don´t force your voice or push, do them gently and playfully. They are healthy for your voice and give your vocal organ, the larynx, a nice workout.