cannot streamline music tracks on a USB FD.

[tomx2x]

Hi.

I have a BLU studio xl2 phone that has reached the internal storage limit.
About 6GB is used by my music tracks.
To get more free space, I want to move the music folders to an portable external FD.

Tested 1 folder putting to a external FD. Then went to settings/storage/USB. Selected USB using OTG adapter having the FD.
Next I played it using MX player, or Google Play music.

The player stopped after playing the first track. It did not streamline down to the next music tracks.
If i just launch MX music player app, it does not see the usb FD with the OTG adapter.

Is there a alternative solution, using a music player or settings I can try to streamline my tracks to play continuously on a portable USB FD using OTG adapter?

One idea I can do is UN-merge the phone internal & SD card. Format SD card as portable, Then load the tracks onto the SD card. I believe MX player will see SD music storage.
The only downside is loosing all my data and apps stored on the SD card.

Thanks.
TC.