Kind of an odd question. why not buy the i7-4790k?
more distinctly back to your original question, do you plan to overclock your CPU since you are asking about the K series CPU's? The i5 I believe overclocks better. If you plan to run at stock I believe the turbo frequencies are faster on the i5 as well. In some cases the hyperthreading can limit overclocking as well. The only advantage the i7 has is the hyperthreading. To answer your items more specifically
Gaming - wont matter (video card is far more important with those CPU's) slight advantage likely would go to the i5 in this case
You tube - wont matter, it will record regardless of what cpu you have slight advantage to the i5 again because of single core advantage
music production - depends on application, there may be a slight edge to either CPU dependent on package and task.
video editing - same as music, but I would venture to guess in most cases it comes down to fastest clock over 2 CPUs (if the application utilizes hyperthreading well, there may be a slight advantage to the i7)
cant go wrong with either CPU for your task list. both would serve you well but if you insist on the best of both worlds the i7-4790k has the advantages of both CPUs with less penalty (except price)