bluesunlasergunfrom what i've read, they aren't great at blocking outside noise, they let plenty of sound leak in. whether they're optimal for singing is another thing though
bluesunlasergunI wouldn't use these for mixing and mastering, as they aren't particularly neutral. For mixing and mastering I'd ideally go with good monitors first, and if I had to use headphone, something ultra neutral, like a HiFiMan HE-6, Sennheiser HD600, or Oppo PM3. If you are buying them mostly as a "fun listening headphone" first and are wondering if you could also mix and master with them, in a pinch, sure. I wouldn't buy them expressly for that purpose though, as you will cause your mixes to not have enough bass, too little 8 kHz and too much 4kHz (ie the inverse of the areas the THX00 is strong in).