Private Music Lessons
I wholeheartedly agree with Stephanie Judy's position that tone deafness is a myth. She makes this clear in her book, Making Music for the Joy if It.
If you struggle with singing, you were probably deprived of supportive and encouraging opportunities to explore singing. You may have become timid due ridicule and unfriendly laughter, but as with most skills, there's no way to learn without making mistakes. Good teachers respond to mistakes by providing more opportunities and by outlining attainable steps, and guiding you through those as many times as necessary.
Still many people belief that tone deafness acutally exists, and that those unable to sing in tune suffer from some sort of insurmountable musical shortcoming. I'd say the true obstacle is any shortsighted instructor who lacks the creative skills and tenacity needed to lead someone through a land of uncertainty (and possibly fear) to a place of clarity, confidence and accomplishment.
Don't believe it
If you can speak and converse, then you are not tone deaf ... even if you haven't yet learned to"carry a tune." This article explains why.
It stands to reason, a person who can't hear pitch would probably be unable to understand spoken language. He or she might be able to recognize individual words, but it's unlikely that the meaning of sentences could be understood.
Consider the following two sentences: "You did fine," and "You did fine?" Each contains the same three words. The only difference between the two sentences is the spoken pitch. The voice lowers throughout the statement "You did fine," offering an expression of reassurance. In the second example the pitch rises through out the length of the word "fine?" thus conveying a questioning expression of surprise or disbelief.
Linguists know that the meaning of sentences change dramatically depending the pitch inflection of various words or phrases. (For instance, as we all know, in English most questions end with an upward inflection).
We constantly rely on pitch recognition to convey and determine meaning. In order to converse fluently you must be able to hear pitch and speak with pitch. So it follows:
There are many instances of pitch in our everyday activities. People sing musical intervals without even knowing it. For instance, when a person hollers out the supper call, "Amy! Dinner!" invariably they sing each pair of syllables in a descending minor third. Ask a self-proclaimed "tone deaf" person (anyone who claims they can't sing) to give a friendly call to their pet from afar. When they yell out the name, "Skip-per! Skip-----per!" they will probably sing a perfectly pitched descending minor third. And if they call twice in a row, they may transpose the minor third a whole tone higher as they "sing" the call the second time. (People don't always sing this a descending minor third when calling but the longer they hold the first syllable, the more likely they will.)
I find it astonishing that the notion of tone deafness ever took hold. If someone has been deprived of the joyful experimentation required in acquiring a good singing voice, naturally they will have trouble on they're first attempts. But to label them as incapable and tone deaf is entirely shortsighted. If a child were raised by wolves and therefore unable speak words, we wouldn't label that child as deaf.
Granted, there are indeed extreme cased where people are truly unable to discern pitch, or where people fail to appreciate music in any way, because it just sounds like noise to them. But this is another story entirely.
What happened in school
In their youth many people were labeled "tone deaf" by teachers and choral directors. I've heard so many sad stories. Like the music teacher who asked each student to stand up in front of the class and sing, to determine if they were qualified to practice along with the class. After their first try, those who failed to perform well were told, "When we practice and perform, don't sing! Just move your mouths and pretend to sing! The rest of us will carry it."
Indeed some students performed poorly during their singing examination simply because they were nervous; not many people sing their best when asked on the spot to stand up and sing in front of a group of their peers. Probably few of them had ever sung solo before. (Speaking in public is a very common and deep fear; singing probably naturally more so.) Other kids probably failed when the teacher forced them to sing outside of their natural vocal range, or simply because they couldn't quickly find the first note! And some failed simply because they had never heard the song perhaps they'd been absent the previous day when it was taught to the class. Life is unfair at times, but one would think that music teachers would proceed more cautiously before branding people. Perhaps something like this happened to you. If so, it's truly a shame, and most likely a mistake.
I knew a teacher who labeled those she deemed "tone deaf" as "grumblers". She dispensed a firm admonition that they remain silent—yes, the very ones who most needed singing opportunities never got the chance to practice singing during class! Words and opinions such as this teacher's have discouraged and excluded countless people from developing their musical voices, they made people feel deficient, even though they possessed unlimited potential.
Living under the belief
Later in life, out of the shadow of the disbenevolent authorities, some 'grumbers' try to sing. When they do, indeed many find that they have less skill than their peers did long ago. But is probably because their classmates had lots of practice; they didn't. Unfortunately, at some point, many conclude that the teacher was right -- that they aren't good singers.
For many, so it goes throughout life. Their undeveloped potential keeps them from trying, practicing, and participating. Lack of participation keeps them from improving.
How were these students ever to improve under the imposed "lip-sync" restriction? What if a math teacher asked each student to solve a single math problem on the board in front of the class? And of those who struggled to produce the correct answer, what if the teacher instructed them, "You don't do math! Just wiggle your pencil while the rest of us study and work." Clearly this would be a case of a teacher failing to perform his or her job. But somehow, year after year, countless music teachers have brushed aside the very students who needed attention the most.
Starting over and setting your own path
Much like our innate ability to develop language, people have an innate ability to sing, but for most it flourishes merely by good example in a supportive environment, and these skills are most easily achieved at an early age, just like learning language. And it is never too late.
Whatever the case, if for any reason you think you can't sing, or if you've been told you can't, don't believe it. It is a skill that you can learn — and you can do so at any age! Don't let anyone tell you otherwise. Even if you think your speaking voice is unbecoming, don't doubt your potential for singing. I've heard individuals with speaking voices that did not sound particularly pleasant, and yet they a fantastic voice in song.
If you pursue singing but have trouble learning to use your voice, have faith. You just need more opportunities, perhaps some good guidance, persistence and patience.
Most musicians don't have it. It's not terribly important to try to develop this skill. However, I suspect it would not be difficult to learn at an early age. Think of how often we ask children, "What color is this?" They easily learn a wide range of colors by a very early age. If we were to play a few notes on the piano every day, and ask the child "What note is this?" they would probably easily learn the notes of an octave, and then progress to other octaves.
Do you have to be able to sing to play instrument, particularly one like violin?
Many people think that if they are unable sing well, instrumental music is out of bounds. They avoid instrumental music because don't enjoy singing, and because they don't want to try to learn to sing. While you don't have to sing to play a musical instrument, it's very helpful, on many levels. Nevertheless, I've known many people who don't sing, and won't sing, but make great strides with a musical instrument, even violin.