Group Membership During Site Registration Possible?

Using Drupal 7. Am a newb, so please bear with me. I believe there are likely a lot of ways to approach this problem and I'm not seeing the best way, or any way : (

I am building a custom social network for musicians that is based, currently on Organic Groups. On the site I have setup a bunch of groups already, that include:

Musicians
Bands
Instrument Makers
Agents
etc.

I'd like to have the user gain membership into one or more of the groups upon registering for the site.

The user experience I'm thinking would work best would be:

1. New site visitor clicks on the 'Register' link for site.
2. They create their site profile (I'm using Profile2 fields that ask lots of additional questions).
3. A list is presented within the site registration form that allows them to select one or more groups (from the list above) to join.
4. User submits their profile and then has access to the groups they selected.

Ideally, aside from an email verification (to ensure they aren't a bot/spammer), I'd like them to immediately be given access to the groups they chose and not have to go through a 'request' process, but at this point I'm open to having to manually approve group memberships if necessary. So long as the user can request the memberships via their site registration form.

What is the best way to approach/solve this problem? I can of course create new profile fields for the various groups but they aren't tied to the Organic Groups themselves. Hopefully there is an easy way to do that so that the user can join groups via their profile page?