I would add a short string property to the SoundcloudPageType and let the users paste into that field.
If you are using PageTypeBuilder something like this:
[PageTypeProperty(
EditCaption = "Soundcloud Url",
Type = typeof(PropertyString),
SortOrder = 2010,
UniqueValuePerLanguage = false,
Searchable = true)]
public virtual string SoundcloudUrl { get; set; }
Then you could either fetch "on request" or fetch and store (easiest on other properties you've added) in one of EPi's save events. Take a look at Joel's article of common patterns when integrating with EPi: