You'll need to use email scripting to implement this: Email Scripting » Marketo Developers The first example on that page demonstrates a very similar scenario.
Check out my blog on a similar topic here: http://developers.marketo.com/blog/make-a-marketo-form-submission-in-the-background/ You would want to use the MktoForms.whenReady metho...
Soundcloud has a widget api (Widget API - SoundCloud Developers) so you could use the javascript callbacks in it to send listening info into Marketo. That actually sounds awesome....
I guess the obvious question here is did you increase your send volume? Are there any differences between emails pre and post, like certain common links having "mktNoTrack" or some...
The conversion will clear out all your data in that field. You'll want to export everything in that column to back it up and then reimport it once you're down with conversion. This...
You're looking for Describe Lead. You can interpolate the display name of the response with {{lead.<display name>}} for the tokens you wish to insert.