You are able to proceed to an account deletion Soundiiz and removed all saved datas on Soundiiz servers at any time directly in your user settings.
If you have created a Soundiiz account with Facebook/Twitter/Google, you will have to use a Soundiiz password to confirm the delete process. You can generate a Soundiiz password on this page.
Be aware that deletion will remove your Soundiiz account and datas but you will have to revoke each access you have granted to a music service to Soundiiz directly in the music service interface.