[Five]

yes, if it was your equipment it should be steady not fading out with the commercials. so it got in there sometime before the commercials were edited in.

could be a ground loop or something coming from a faulty/cheap pickup/amp during the gig or the equipment used to record the gig ... not certain.

bass amps are often the offender, inserting a di and lifting the ground or some other transformer setup can cure this, sometimes changing which outlet the plug is plugged into can also work magic.... of course, this isn't much of an option after the fact. The stripes can be attacked using the surgical precision of an fft filter or nr applied only on the very narrow band where it is necessary, however beware of how wide and deep the settings are or else you run the risk of creating a "black stripe" lol. Generally, leave it alone unless you're 99-100% confident about what you're doing. I have a couple tutorials on this topic somewhere on my computer and can dig them up and post them if there's any interest here.

There was one act I was doing sound for at an outdoor fest and the bass player had such a bad buzz coming from his amp we actually were muting him between songs since that's when it was most noticeable. We tried everything we could think of to get rid of it another way but time ran out and as they say the show must go on.

Another show I was at in January had some steady high-pitched noise in the audio, kinda like a buzz but more high-pitched like an "eeeeeeeeee" sound audible in the room at the time. I didn't get a chance to troubleshoot the system (I was just attending), but the stripes still showed up on the open-air recording. ps it was not my recorder causing this as it was only on that show and I recall hearing it in the room.