I am using Rekorbox on Windows 10 with the DDJ-RX.
Originally, when I installed Rekordbox, I went into the preferences and set it up for sound to come out of the DDJ-RX and not the computer. When I did this, it also somehow automatically disabled all other computer sounds. I could not play anything from iTunes, and if my computer produced a notification, it would be visual only, with no notification sound.
Another thing: If I shut down Rekordbox and reopened it, the setting would automatically stick.
Starting a few months ago (maybe it was after a Rekordbox update, maybe a Windows update, I don't know), I started noticing two things:
(1) Every time I open Rekordbox, I need to go to the preferences and change from my PC sound to DDJ-RX.
(2) Computer system sounds play over Rekordbox. This is AWFUL! I have gone into the Windows sound settings and disabled everything possible other than Rekordbox, but the problem is that the Windows sound settings only show options for programs that are running at that time. If a new program is opened, or if a new notification comes in, it will play over Rekordbox.
Last week, I was DJing a wedding. Someone sent me a text and my Messages were open in Chrome. Sure enough, a loud chime played over the music and everyone glared at me. Not fun!!!