Thanks, guys, for your kind comments.
I have just checked, and music which was ripped from cd and nicely foldered up is playable in sequence using the resident file manager.
When I let the Enjoy Music Player app find the same music, it displays the tracks out of sequence and interleaved. So I have Schostakovich Cello Concerto No 1 in random sequence, interleaved with Schostakovich Jazz Suite No 2 in random sequence.
Reviews of the Kubik Evo mp3 player report similar problems with classical music.
Pop music and jazz also get scrambled but of course it really doesn't matter to the listener what the track sequence is. On Classical music, Mr Mixture, it does matter, one wishes to hear the movements in the correct sequence.