Need to add media with embed code and NOT URL - how to do it?
Create a new field on your content type called "Embed code", and create a new text format called "code" where HTML is allowed, and no WYSIWYG modules are enabled.

Use css to change the width and height of the iframe of the soundcloud widget. it will adapt automatically.

More control Using Views:


Hide that field from display on the "manage display" tab of your content type.
Create a view block display.
In that view, bring in the embed code field.
Add a contextual filter to the view. Use the nid and provide a default value "content ID from URL".
Place the block on your page.