Thanks for any help.
Selecting an mp3 filevia Open LP media will allow it to play but with a black screen. Themp3 file can be added to ppt slides.
Soundadded to 1 slide will play while the slide is shown. It stops playingwhen the next slide is shown.
InLibreOffice Impress ( ?Powerpoint?) it is possible to have the soundplaying continuously whilst a series of slides are shown. To addsound to a ppt. Insert> movie & sound>> rt pane slidetransition> sound>other sound; browse to sound file subsequentslides <no sound> till last slide when <stop previous sound>