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
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!