You can cancel your Membership at any time, whether it be Annual or Monthly. You'll still have all of the benefits until the end of your billing cycle. (If you bought an Annual Membership in March, and cancel in August, you'll still have it until the next March. Likewise, if you bought a monthly on March 4th, and cancel August 19th, you'll have it until September 4th).
Once you cancel, you'll have only the Sampler. This means that any playlists containing Membership-only work will be removed from your Canvas as well as your account.