The introduction of iTunes was massive because it allowed consumers to digitally purchase an individual song instead of being forced to purchase a physical copy of a whole CD, after Apple introduced iTunes this style of music distribution took off like wildfire and now nearly everyone uses it so I would say it did indeed revolutionize the music industry.
I believe that the invention of iTunes did change the music and tech industries forever. I think that when iTunes was made popular, the music industry discovered a new way to sell their music and distribute it. I think that technological advances in the music industry was also beneficial for a lot of artists to sell their music.
The invention of iTunes has enabled people to go on the internet and buy and listen to what ever music they want to and when ever they want to from the comfort of their home. As a result there is less sales in music stores and less people listening to the radio.
I'm not sure if it changed the tech business so much, because there were services similar before the invention of iTunes. But it definitely changed the music industry, because with iTunes, the technology became much more known world wide. This, in turn, is what caused the actual revolution in the industry.
Yes, the invention of iTunes changed the music and tech industries forever, because it gave us a way to get our musical legally on the internet. Anymore, we do not have to buy an entire album. We can pick and choose to buy one song if we like it. We have a new way to get music that has made the music industry step up to offer quality.