tomasc, Thank you for your prompt reply, the excellent and helpful advice and for introducing me to a part of PD14 I had not previously explored. I can now control the level of added music as I would want to. After a number of years of producing DVDs, I am now getting more adventurous and am entering the field of added music. The next phase will be, where appropriate, voice over instead of subtitles.
In gratitude, Samuel MacKenzie