When you open the map in your Radiant you will probably or hopefully get the impression of some kind of jungle/island theme. Well if you do a final compile it looks okay, but there are definitely missing some sound effects and a music.
Let's start with a simpler task: the music. We want to have a looped background music, which volume we can control via the menu's music dialog. There is music in every Quake 3 Arena level. Listen to it. It rocks (made by Sonic Mayhem -> http://www.sonicmayhem.com/music.html).
In the editor select a brush which is no entity and press n.
You will get the worldspawn dialog. Type in "music" as key and as value
the exact path and filename of the music file. You could either use one
track from the original game or the one which comes with the pk3 (of
course I recommend this one). Or try one after another.
The path always starts from the baseq3 folder. Type in: "music/sonic4.wav" (which you can find in the pak0.pk3) or in our case "music/speakertut_loop.wav".
Of course you can put the file where you want, but I suggest to keep the structure and put the music into the "music" folder and the sound effects into the "sound/name_of_my_map_here" folder.
In general the music set in the worldspawn is always played in a loop (means, when the file is over it starts again... so be sure your music can be looped) and everyone in the game can hear it. It can be regulated over the music handle in the sound options or over the console (s_musicvolume). The music plays from the beginning on you spawn.
Transitions like in Serious Sam (peace/war music) can't be done in Q3A.
Now compile the map and listen to the music.