In GarageBand, choose Share > Mail.

In the Mail dialog, do the following:

• Select Project, if you want to share a project that recipients can open and edit it in GarageBand on another Mac.

  All audio-related settings are unavailable.

• Select Song, if you want to share an audio file mixdown that recipients can open and play in iTunes, or any app that supports .m4a files.

  You can edit the following settings:

  • Enter a new name in the Title field.

  • Choose an audio format from the Quality pop-up menu.

  • Choose whether to bounce the entire project, or only part of it based on the cycle area or the length of selected regions.

Click Share.

If a mail account is available, a new email is created.

The project or song attachment will be delivered, even if the size exceeds the maximum allowed size for attachments.