Keep in mind that the notion of a song being “in” a key is just a convention applicable to music that follows certain rules. A song that doesn’t play by those rules would be harder to assess, and yours, at least to an extent, doesn’t.
That’s not to say that they are arbitrary rules. It’s more of an uphill struggle to compose stuff that we actually like to hear without conforming to these patterns at least somewhat. Our ears tend to like songs to hover around a key structure that it calls “home”, and to revolve to an extent around major or minor variations of one, four, five, & six. But for the sake of argument, you’re going to have jolly fun deciding what key a piece is “in” if the predominant chords are D major and A flat major (with the melody line doing cute things like staying on the same note while the supporting chord structure shifts underneath it and then heading off in the new key). If all you had of Bloodrock’s “DOA” was the verse, not the chorus, you’d pretty much be in that situation. Calling (and writing) the A flat stuff as G sharp major would be possible but wouldn’t clear up matters much.
As I said, though, our ears like matters a lot better if even weird and esoteric music comes home to rest, and “DOA” is not that much of an exception. The chorus gives you sufficient reason to toss the whole works into the first of the two offset major keys (I don’t know if it’s really D and A flat, but that’ll do as example, and in this example it would be D = the key it’s “in”).
You’ll notice the assumption that individual chorded notes or passages, at least, are “of” a definable chord-key. That, too, is a convention, one that normally applies (and which, again, our ears tend to prefer to the alternative) but not every pattern of concurrent pitches overlaid upon each other is going to yield a chord we could readily name, and it is at least theoretically possible to write a song that has none (or few of them, and with no discernable step-pattern between them), and under those circumstances you’d really be hard put to establish what key the piece is “in”.
::pauses to think of an example::
::which proves to not be so easy, illustrating my point::
Hmm, OK, Pink Floyd’s “Sisyphus Part 3” (3 short excerpts), from the album Ummagumma. Try writing out the chords for that sucker! And as a consequence of the difficulty of that, you’d be hard put to determine what key the piece is in.