Playing music files on USB drive

I’m using DietPi on a Raspberry Pi 3 with an IQAudio Dac. I’m trying to play music files using Mopidy. When I plug in my USB Flash drive with the music files on it and mount the drive in DietPi I loose my connection to Mopidy. Is there a way to play the MP3s on the flash drive some other way than using DietPi’s mount option? It looks like when I mount the flash drive in DietPi other running processes in DietPi are shut down and that’s why I’m unable to connect to Mopidy from my laptop. Am I right on this? Any help you could give me would be much appreciated. So far very pleased with DietPi and the sound quality of the music files is great. Thanks.