Apollo Sound Injector makes it easy to stream audio from one iOS device to another. Use the app Sidecar with the device that is sending audio, and Sound Injector on the device that needs to receive the audio -- we have two separate apps so that it's easy to know which end is which.
Both Sidecar and Sound Injector work with Inter-App Audio, so you can integrate iOS synthesizers and sequencers, and build complex audio processing chains. And if you're making music, you should also take a look at Apollo MIDI over Bluetooth -- the fast way to send MIDI between multiple devices.
Secret Base Design has years of experience developing leading edge apps for serious musicians. Our "Apollo" series of apps are designed to let you use multiple iOS devices, as well as desktop and laptop computers, to build an integrated and flexible music studio.
If you are using desktop DAWs, you can take advantage of Sound Injector on the desktop.
Note that with audio streaming over WiFi, there can be some latency, and performance will depend a great deal on your router, and the WiFi traffic. Sound Injector features a novel latency reduction algorithm -- but there are limits to how far this can go, and very low latency connections may also introduce audio glitches.