On Android, I use Music Maniac. It is the best downloader I've had yet. Every song I've downloaded from it (a **** ton) has the artist - song title and album art all correctly formatted so you can have an organized music library. Also, they have all been of cd quality. I've been able to find most everything I look for with this app, and being into the metal genre, most of what I search for isn't just extremely popular, yet has been readily available. What I've found works best is to put in the artist's name and the title of the album and it usually brings up every song from the whole album. I give it 2 thumbs and one big toe up.
PC, I use MP3 Rocket...It's about like Limewire was and in my opinion, better than Frostwire, as I switched from Frostwire to MP3 Rocket (free version). It can pull MP3's from Youtube, so if someone has it uploaded on Youtube, that MP3 file will be available in the search results. Also allows you to preview song prior to download, which is a big deal to me, as I cannot stand a shitty quality song. I'd just rather do without a song if it were anything besides cd quality.
I don't download on my PC much anymore since I have bluetooth in my tow rig now and MP3 cord in my crawler, I always play music from my phone. I still rock CD's in the Saturn, but I've got a ton of burnt CD's to suffice.