It will play from a flash drive. It will play them from an external HD as long as the external is plugged into the USB port that says <powered> It has 2 USB but only one is for the external.. the flash will play music from both.
I have the 42" version of this TV. My TV has 1 USB port but I cannot answer yes or no regarding playing music from a flash drive. In my opinion, the speakers aren't suitable for good clear music audio.
I can tell you POSITIVELY that it plays MP3 from the USB and using my flash drive. i just tried it! but if you can tell me a SPECIFIC file i can put it on my flash drive and test it out and let you know. i haven't downloaded any files on my computer or phone in FOREVER. so i don't know what is out there and what's not as of late. i'll wait for your response.