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
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.