Customizing the feed for a specific category

In some of my posts (category: music) the only content is a youtube video. Unfortunately, not all rss readers display the video. That’s why, in the feed for this category, i would like to replace the content (the video) with some text, for example “Visit our page to watch the video”.

I believe, there are three approaches to my problem:

1) customize the feed template (wp-includes\feed-rss2.php). I don’t want to edit core files, so that is not for me.

2) create a new template (described here) and customize it. This works fine for my main feed (http://mysite.com/feed/customfeed/) but won’t work for the category feed (http://mysite.com/music/feed/customfeed/). Any ideas why?

3) use a filter. I have no idea (and no programming skills) how to make this work. I imagine something like this:
if is feed from category 3 remove filter the_content and add text “Visit our page…”
Is this possible? Is this a good idea?

Any help will be much appreciated.