There must a spelling mistake in Cyberduck... 
Uploaded in a new ftp client and that immediately fixed the issue.
Jeez ... Totally sorted. Thank you Klaus.
** Head removed from screen ** 
Cyberduck had set the right permissions on .js and .swf files but it just didn't work... so there's something very peculiar with it.
Avoid if you can.
Can't help but think this is some school boy error...
Have built the same in versions:
1.16.4
http://mouthtosource.net/portfolio_medi…n_cube_005.html
1.16.9
http://mouthtosource.net/portfolio_medi…_4/bayon_4.html
1.0.8.15
http://mouthtosource.net/portfolio_medi…n_cube_006.html
All run locally.
All exhibit same load error...online.
ERROR: download of "plugins/soundinterface.swf" failed
ERROR: download of "plugins/soundinterface.js" failed
All krpanoiphone.js are relevant to each version of krpano and in the right folder.
Same method... droplet pano multires... create folders for audio, graphics...
xml copied from background sound example 1.17.5 and amended to allow for folder structure (audio/graphics).
How do I fix? Pleeeease. It's a feature I really do need...
Many thanks in advance.
Forum,
I'm sincerely embarrassed to post here again covering the local and online issues that keep cropping up over background sound deployment. Doubly so because I actually did an example a couple of years ago and it worked on desktop and iOS.
I'm stumped, have read every post already on the forum and am so close to sticking my head through my macbook. If you could save a Macbook. I'd be eternally grateful.
Here's my methodology...
In krpano 1.16.9 I've made single (multi res) pano in with the droplet.
Copied soundinterface.js and .swf to new folder called 'plugins'. soundonoff.png into a new folder called 'graphics'
Pasted in the background sound code from the example provided in latest download (krpano 1.7.5) and amended urls to accommodate new 'folders'.
All hunky dory locally...
Online I get the dreaded...
INFO: krpano 1.16.9 (build 2013-10-28)
INFO: Flashplayer MAC 15.0.0.152 PlugIn
INFO: registered to: Paul Stewart
ERROR: download of "plugins/soundinterface.swf" failed
and a similar response from iOS to say it can't load the soundinterface.js
URL is here...
http://mouthtosource.net/portfolio_medi…_4/bayon_4.html
xml is this...
<krpano version="1.16">
<include url="skin/defaultskin.xml" />
<view hlookat="0" vlookat="0" maxpixelzoom="1.0" fovmax="150" limitview="auto" />
<preview url="bayon_cube_005.tiles/preview.jpg" />
<image type="CUBE" multires="true" tilesize="512" progressive="false">
<level tiledimagewidth="2028" tiledimageheight="2028">
<cube url="bayon_cube_005.tiles/mres_%s/l3/%v/l3_%s_%v_%h.jpg" />
</level>
<level tiledimagewidth="1024" tiledimageheight="1024">
<cube url="bayon_cube_005.tiles/mres_%s/l2/%v/l2_%s_%v_%h.jpg" />
</level>
<level tiledimagewidth="512" tiledimageheight="512">
<cube url="bayon_cube_005.tiles/mres_%s/l1/%v/l1_%s_%v_%h.jpg" />
</level>
<mobile>
<cube url="bayon_cube_005.tiles/mobile_%s.jpg" />
</mobile>
</image>
<!-- load the soundinterface plugin -->
<plugin name="soundinterface"
url="plugins/soundinterface.swf"
alturl="plugins/soundinterface.js"
rootpath=""
preload="true"
keep="true"
/>
<!-- start playing the sound -->
<events name="currentpano"
onnewpano="playsound(bgsnd, 'audio/pop_gear.mp3', 0);"
onremovepano="stopsound(bgsnd);"
/>
<!-- button to pause the sound: -->
<plugin name="snd" url="graphics/soundonoff.png" align="leftbottom" x="10" y="10" alpha="0.25" scale="0.5" onover="tween(alpha,1);" onout="tween(alpha,0.25);"
crop="0|0|50|50"
onloaded="if(ismobile,set(scale,1));"
onclick="pausesoundtoggle(bgsnd); switch(crop, 0|0|50|50, 0|50|50|50);"
keep="true"
/>
</krpano>
So I figure everything is in the right place... but why is it not working online? 
Many thanks if you can point the finger at the offending article/method/comma or backslash.
p.s. Now to add another twist... if I move the folder over to my iPad 2 from Macbook via AirDisk Pro... it actually plays on the iPad2. When I hold my finger on the .html it doesn't however give me an option to open in Safari (but that perhaps is another story).
