Harmonix has released a list of legacy instruments which will be compatible with Rock Band 4.
PS4 users will be able to use nearly any previous instrument out of the box - even from the PS2 Rock Band games - provided they can find the USB dongles that came with them.
However, the Xbox One version of the game will only work with wireless instruments, and only with an included adapter.
That hardware adapter is the reason why the Xbox One version costs more than its PS4 counterpart.
All previous wired microphones are compatible with all versions of the game.
The band-in-a-box version of Rock Band 4, including new instruments, releases 6 October for AU$499 or NZ$529.
Check your instrument compatibility below.