So you want the seekbar to start on each layer to show the length of each layer and to not be seekable? Don't think you can do that.
But, I agree with Tom, if you are not going to let them 'seek', don't use a 'seekbar', it seems confusing to have something that typically would allow you to seek. If you just want to show length of layer, or video or audio or whatever, use something else like an animation or even just a simple text box that says how long it is.
Also, your SME could try to make the audio more interesting/meaningful if they are worried the learners might skip it. ;)