Let's say someone can sing in tune and doesn't have any bad sounds to their voice - but their tone is simply not that nice/interesting. How can they work on their tone to develop it... what actually is a singer's tone and to what extent can it be deliberately shaped in a particular direction rather than being unique to that person?
Philosophically, I believe my best possible tone is the most open and honest sound of my personal voice that I can achieve. Instead of shaping my sound, I view it as finding my sound.
I try to find it by:
- Warming up (this is so key to singing and more important every year you get older)
- Staying in my comfortable range - at least while working on my sound
- Striving and listening for the most clear-sounding and relaxed technique with the best intonation and maximum chest, throat, and head resonances
- Avoiding the desire to have any specific sound or genre
- Avoiding using other people's diction or accent on the lyrics - the biggest leap forward I took in my own tone was when I imagined myself saying the words the way I normally would, but with a specific note from my voice box instead of my normal speaking "notes"
The last point I'll expand on slightly: If you listen to popular singers, they often have unusual ways of saying things. The lead singer of Third Eye Blind actually sounds like he has a lisp half the time. Lots of singers have Canadian or British or Southern or California accents that are not obvious but do affect how they form the words. It helps to form the words the way you form them.
One way to set your diction and accent in your mind for singing is to say the lyrics in your normal conversational voice, and then sing them right afterwards in the same style. Look out for unusual pronounciations by the people you are listening to and avoid imitating that.
I did most of the work of finding my sound at a karaoke bar. I picked songs that I knew right down to my bones and were comfortable for me to sing, and then I focused on opening up and sounding like me and no one else.
If you can write your own lyrics and melodies, that can help a lot, since your brain won't be hearing anyone else's voice when you are singing your own music.
A tone is something you can work on in different ways. For example, if you try different styles of music, you will notice your voice sounds different when you sing blues than when you sing pop.
You can also try singing in different emotions. When you sing in a happy way, your singing will sound light. When you sing in an angry way, your voice will sound heavier.
Or try to listen to different artists. They all have a specific tone. At first, you can try to imitate what they are doing, so you can experience some different ways of singing, and try to figure out what you like.
In conclusion, just experiment with your voice! Don't be afraid of sounding very weird... We all do that from time to time. Try different styles and emotions, and keep practicing! Then you'll get there.
Get some lessons from a voice teacher. There is no substitute for this. You need real-time feedback from a professional who can critique your tone and show you ways to improve it, over several sessions. Try to find a teacher sympathetic to your personal goals as a singer, and who is willing to give you several lessons on a short-term basis in order to help you figure out what you want to do and how to achieve it.
The question is subjective. What is a nice/interesting tone? You and I can differ on that. To work on changing or improving tone I think it is all based on experience. Just like playing a guitar solo, you will sound not quite right if you don't practice and pay attention to every little detail. I have been working on vocals and copying the sounds vocalists make and I believe they are so experienced and relaxed that they have that 'lead singer' tone. They are comfortable to the point where they don't think about what notes to sing, it is just natural to them to sing the words in a melody with qualities like vibrato, dynamics, grit, etc. Some are born with a natural ability and others may not get to a satisfactory level no matter what.