From Boss:

The Bluetooth Audio MIDI Dual Adaptor (BT-DUAL) is a compact adaptor that brings Bluetooth audio and MIDI capabilities to compatible BOSS and Roland products. Once installed, you can pair with a Bluetooth device such as smartphone or tablet and communicate wirelessly with the product. The actual wireless functionality thats available depends on the specific product model, but it may include music streaming with Bluetooth audio, controlling various product functions with Bluetooth MIDI, and more.

Standard Features

• Brings Bluetooth wireless capabilities to compatible BOSS and Roland products
• Supports Bluetooth audio and Bluetooth MIDI (BLE-MIDI) communication standards
• Quick and easy installation
• Power supplied from the host product