Ugh!

My wife noticed a "musty" smell in our bathroom and after investigating I discovered that the shower was leaking. There is an access at the base of the tub/shower that I looked through as my wife ran the faucet. She ran the faucet into the tub for a couple of minutes and I did not see anything dripping. Then I had her divert the water flow through the shower and began to see drips.

The house was built in the late 70's and I was wondering if the pipe that comes through the wall where the shower head attaches is sweated on the other end (inside the wall) or is it threaded?

I tried to turn it hoping it was loose but it wouldn't budge so I'm not sure what to do next. If it's threaded I figure I can loosen it, remove it and maybe tape it with silicone tape and hopefully that's it. If however it's sweated on then there is no option but to bust into the wall to make the repair, obviously I don't want to do that. So, threaded or sweated, that's my question.

Thanks for any help.