The good news is that online voice classes are just as effective as in-person classes. In fact, they can be even more useful if done the right way. Online classes aren't as effective, but almost as effective as real-life ones. And they can be useful in a practical sense.
In the end, online singing lessons are a great tool to take you to the next level. Do online voice lessons really work? I personally took singing lessons for many, many years. I bought courses, DVDs, books and met with almost every local teacher I could find and saw very little progress no matter how much time, money and practice I spent on it. I went to the woodshed every week, practiced my duties and scales diligently, tried various approaches and experimented with several different methods, but nothing seemed to work for my baritone voice.
Vocal teachers can show you tried and tested techniques to make you sing louder and in tone. For those of you who are undecided about the idea of learning singing skills online with a vocal coach, it's helpful to point out some of the positive features of online voice lessons. The bottom line is that the success of the lesson depends on both the teacher and the student, as in live face-to-face classes. It also gives you an even greater chance to find someone who shares your same passion for the music you like to sing, someone who can tune your voice when singing in the direction you want to go and someone who perfectly matches your vocal range and style.
If you have a stable internet connection, a webcam and a good microphone, there's no reason why you can't take advantage of online singing lessons. I should mention that it is not necessary to be on a desktop computer, several of my students have done their classes through their smartphone with a great connection. As you take singing lessons, you'll find out exactly what that range is, as well as which songs fit your comfortable range best. Saving time and money means you're more likely to fully commit to your classes and less likely to cancel them.
I have been training to detect difficulties in the voice, and it is possible, I would say 90% of the time, to do it online as well. The other big advantage of taking individual singing lessons was that the teacher was able to give me feedback immediately after doing something wrong. You'll learn how to adopt good vocal health, how to use your whole body to complement your singing, and how to take advantage of the right techniques to get the best out of your voice. Whenever you need a higher level of personal attention, you can travel for an occasional real-life lesson.
However, once you have a little knowledge of singing and you try to achieve clear goals (even if they change over time), there is no substitute for in-person singing lessons. If your technological skills are very limited, if your microphone decides not to work or if your webcam is in the blink of an eye it could be a very frustrating lesson. If you mean taking a lesson with someone via skype or other video chats, I think they can be very useful.