You can keep your Splice folder on an external drive, but we do recommend keeping your Splice folder saved on your local hard drive.
If you decide to keep your Splice folder on an external drive, make sure you're always connecting your HD before starting up Splice, and closing Splice before disconnecting the HD. We also recommend not making the Splice app a launch item upon starting up your computer.
If the Splice app ever runs without your external drive connected, the app will automatically create a new Splice folder once you start redownloading or adding samples to your Library in one of the default locations. You'll then need to re-link the desktop app to your Splice folder on your external drive.