What is mastering?

Don't you hate these pedantic sermons that every mastering website seems to have? I do too. Let's be honest, mastering is mostly compression and EQ. Just like mixing is mostly compression and EQ. Why do you need both? You wouldn't let your primary care physician operate on your brain, would you?! And that's essentially the difference: Mastering engineers specialize in this one thing, and we are equipped with special tools and techniques to get the job done right. Mastering engineers are the neurosurgeons of audio production.

Do I need mastering?

Are you creating a recording in the hopes that people will listen to it? Then yes, you need mastering! Mastering is the optimization process that makes your music ready for playback in the real world... i.e. cheap earbuds, crappy Bluetooth speakers, car audio with obnoxious subwoofers, Beats headphones, and laptop speakers! It is a minefield out there right now. In addition to the standards of yesterday like broadcast radio, home stereo systems, and car audio... your music has to withstand a lot of abuse at the hands of streaming and low quality listening devices. Mastering ensures that you'll sound as good as technologically possible on the very worst — as well as the very best — of mediums.

My mix engineer says he'll master my tracks for a little extra money.

Your mix engineer is a hippie. I am a scientist. Your call.

Do I need a separate master for vinyl?

YESSSSSSSSSSS!!!!! You really do. I'm sorry that it does cost a little more, but you'll thank me later. Every time a client puts a CD master on vinyl, I honestly consider drawing up a contract prohibiting people from doing that. It just doesn't sound good. Here's why: The level of compression and limiting necessary to attain commercially acceptable loudness on a CD or your average digital streaming platform is vastly different than what sounds good on vinyl. Some vinyl duplication services will agree to just "turn the master down" when they press the vinyl, but that does not create dynamic range. CD Masters pressed to vinyl sound squashed, muffled, indistinct, and lacking punch. And frankly, it's really embarrassing for me to have my name appear on the jacket.
I would be happy to make you a dedicated set of vinyl masters. They will sound fantastic, and like a slightly more intimate version of your CD. In addition to having the appropriate dynamic range, your vinyl masters will be EQ'd separately from your CD masters — specifically tailored to be stunning when the needle drops.

Analog vs. Digital Mastering

This one is interesting. Some recordings really do sound better with purely digital mastering. I would argue that those recordings are rare, but it does happen. However, a professional mastering engineer will be equipped with the best in both digital and analog processing. If someone tries to sell you on "in-the-box mastering" because that's all they have, don't waste your money. Digital vs. Analog is not the aesthetic choice it may sound like, it's a matter of preserving and/or enhancing the fidelity of the audio, and it's a choice for your mastering engineer to make.

What about LANDR?

The only instance that I can see LANDR being useful is a true "demo." By demo, I mean a recording that is not meant to be heard by the public. It's a rough sketch of a song to show other songwriters, performers, or a label. On the other hand, if I was pitching my music to Brad Paisley or his label, I'd sure as hell want it to sound its best.