The song titles can be added to your stream using
Text (GDI +) sources, or
Image sources containing pre made images if you want to do more with branding etc.
To create an overlay (or: DownStream Keyer) you make a scene with text or image sources for all the titles you want to show. Have the visibility off (eye icon). Now go to you camera scenes, add a source of type
Scene and set the Overlay Scene you've just created. By setting and resetting visibility of the various sources one by one within the Overlay Scene you can show the appropriate song title.
Showing/hiding the sources (setting/resetting visibility) can be done various ways. Maybe the easiest for you is assigning hotkeys to Show/Hide source. Or have a try with one of these resources:
This Lua script adds hotkeys for Next Scene and Previous Scene, which let you cycle through your scenes in OBS from the keyboard. I use OBS like a slideshow/presentation deck so this helps me cycle through dozens of scenes during a broadcast...
obsproject.com
Maximum 1 source visible per configured scene and group When you make a source visible in a configured scene or group all other sources in that scene or group will become invisible. This way maximum 1 source is visible in the scene or group.
obsproject.com
Download Plugin for OBS Studio to add a source that switches between a list of sources Add "Source Switcher" source to your scene. In the Sources property set a list of source names you want to switch between. Set the switch conditions using...
obsproject.com