This is a question we receive quite frequently and it comes down to understanding the capability of your iOS/iPadOS or macOS device, as well as different types of Bluetooth products and how they work together. But let's answer the question with a simple, yes. Let's take a look at the different kinds of Bluetooth devices and how you can use multiple on a single device.
Streaming Audio
This is a common use case for streaming audio from a device wirelessly. You can pair with multiple Bluetooth audio receivers, but you can only have one active Bluetooth audio device at one time.
Human Interface Devices (HID)
You're probably accustomed to Bluetooth devices like keyboards and mice that let you interact with your computer. Devices that run OnSong can also use connected keyboards, mice, and trackpads. You can pair with multiple Bluetooth HID devices but are generally limited to 7 of those devices connected at once. This may vary, but it's typically enough for most users. Many foot pedals operate as a computer keyboard out of the box so if you're pairing the foot pedal in the Bluetooth section of the Settings app, you are up against that limitation.
Bluetooth Low Energy (BLE)
This type of Bluetooth device is commonly used for many "Internet of Things" devices from fitness trackers to smart watches, sensors to remote controls, medical equipment, and much more. These connect in a different way and usually through an app. Many foot pedals have a BLE or "App Direct" mode that you can pair within OnSong. Once again, you can have many devices paired, but only about 16-20 devices active at one time.
Bluetooth MIDI
While Bluetooth MIDI devices pair differently in OnSong and other apps, they are still Bluetooth Low Energy (BLE) devices so they would be counted as one of the 16-20 devices you can connect.
Foot Pedals
This should answer the question if you can stream audio and use Bluetooth MIDI at the same time along with a foot pedal running in "arrow key mode" as a Bluetooth keyboard. However you may wonder if you can run multiple foot pedals at once. Again, the answer is yes but there are some things to consider.
You'll need to consider the mode that the foot pedal is configured for. For instance, if you purchase two AirTurn BT-500 foot pedals, they both will come configured in the same mode and transmit up and down arrow keys for greatest compatibility. If you use these in OnSong, you'll notice that you can assign actions, but both foot pedals will perform the same actions.
To solve this, you can change the mode of the foot pedal. The best practice is to set one or more of the foot pedals into BLE or "App Direct Mode". This will use Bluetooth Low Energy allowing more devices to be connected. In addition, in this mode you can assign unique actions to each pedal.
To do this, go into the Pedals Screen of the Actions Editor from the Menubar and choose the foot pedal model you are using. You'll need to pair the foot pedal in there and choose App Direct Mode in the Mode Picker. You can then press the physical foot pedal button to open the Choose Action Menu and select an action for each pedal. Repeat this for all physical foot pedal switches.