Reply to Is it a bad idea to play "free download" tracks on a big system ?

So I got CDJs a while ago and I'm burning CDs almost everyday.
And I have got more than a hundred really good tracks that were given away for free by producers.
(Christmas, xyz facebook likes, just because...)

And today I was burning some and I thought, wait a second, this isn't released by a label, so is it even mastered ?
And I contacted the producer and he advised against playing it on a big system. But he was a small time producer.
But I've got a lot of free tracks from big producers like Skream as well.

I've burned more than a dozen CDs with free tracks, but are they useless at a party ?

Tracks given away for free by producers, are they mastered ? Are they safe to play on a big system ?