How do I send a message (email) to members ona speficic level?

We are setting up a membership site which has certain pages available to certain membership levels. We would like to be able to send a message (email) to all users of a certain membership level when we have added new content or have other member benefits happening outside of the system (e.g group calls). Is it possible to send an email to all members of a certain membership level? These would not be pre-timed messages, they would be sporadic and sent out in real time. Thank you!