Music format for bringing to audition/demo


Had my system for 20+ years, time for an upgrade. I have not been in a hifi shop since 2000 and at that time I would simply bring CDs. Nowadays is it most common for people to bring digital music on a thumb drive or some other way and what is that? Or do people rely on dealers having nice streamers and they just look up what you want to hear? 

Basically I want to know what it most common and how I can bring music that say I downloaded from hd tracks or similar sites to the dealer. 
nhb1
I haven't felt the need to bring anything in years. If you have something you feel the need to hear in order to be able to evaluate, then bring what you feel you need. Why would you bring what someone else thinks they need?
If you feel the need to bring your own music when auditioning speakers just bring your favorite music on whichever format you generally use. No use suggesting classical music on reel to reel when you’re a headbanger that listens to MP3’s.
OK I will just bring some downloaded 24bit songs on a thumb drive, just wanted to check what was common or if there's another way I should know of that's better.  
OK so downloading an HD track then copying it to my thumb drive will do the trick then? I am terrible with computers and want to make sure I don't need some program to convert files, I am noob at this hehe. 
A couple of years ago, or a couple and a half, I went through a few stores bringing my CDs and files on a drive. Wherever I went, except one, they had no CD Player readily available and, at that time, it was the same for USB connected files. In all places, except that lonely one, they brought me an iPad with Tidal and asked what I wanted to hear. It just happened that Tidal did not have what I wanted. In the end, I would enter and ask if they had a CD player, rather than ask to check the speakers I came in for.

The only place that was ready for CD and USB drive was.....Crutchfield.

So, nhb1, bring all you have, but expect an iPad.
Before visiting, call the store and ask what they have available for playback.
I never take anything. Every place I go has every song I would want to hear. 
In the past i would carry one or two lp's.
Later a couple of cd's. Now a USB or my mobile.
If i want to stay longer i take all the above and give them a hard time.
Not seriously, no need to bring anything as there is always something there that could satisfy.

G


Bring CDs. And 1 LP just in case they have a vinyl rig. 
What I bring is what I listen and KNOW the most. 

Here's a list I made a few months ago of what I take to auditions...

Gum, mints, toothbrush, floss, tissues, pens/pencils, sunglasses, reading glasses, phone charger, hair bands, bobby pins, nail file, advil, Starbucks gift cards, a book, lotion, granola bars, chapstick, single use Super Glue, eyedrops and some CD's LP's et cetera.

Just kidding, and it's been @ least 15 years since I visited a HiFi shop.

I would call the store to see what source components are available to use.

DeKay
"Gum, mints, toothbrush, floss, tissues, pens/pencils, sunglasses, reading glasses, phone charger, hair bands, bobby pins, nail file, advil, Starbucks gift cards, a book, lotion, granola bars, chapstick, single use Super Glue, eyedrops and some CD's LP's et cetera."

Two-step radius from the check-out at CVS?
Call ahead and find out what they have.  Unless you know what version/quality of the songs you want to use are on Tidal/Qobuz you might be better off bringing your own CD or downloaded version as all recordings are not created equal.  Hell, id even bring my own CD player if it meant I got to hear the right recording, but then i have issues.  Welcome back to the fray!