[File order jumbled]

Thanks for the pointers Andre, especially the recommendation for Tagscanner. Bewildering choice out there.

[File order jumbled]

Yes this is job I need to do. Could you be so kind as to point me to a suitable reference? Thanks very much.

[File order jumbled]

Andre thanks for answering. I'll get onto that.

[File order jumbled]

I have files in two folders 

Bach_Well-Tempered_Clavier, Book I
Bach_Well-Tempered_Clavier, Book II
These show up in Android's Solid Explorer in logical order. (see first pic)
When searched in Poweramp, the order is jumbled. The playing order shown jumps seemingly at random between the two folders. I have the 'filename as title' option turned on in Lists settings.
Thanks.