Choosing sounds
Let's guess what happened. You found that incredible song, which is a mix between electronic and heavy metal and think it would fit really good in your space shooter game. You downloaded it and enjoyed 4 minutes and 56 seconds of Blu-ray quality sound.
Also, in a matter of minutes, you found at least three more songs that would also fit perfectly in your game. Let's add them all, doing an in-game radio like in a GTA series.
No. Wait! The player is running your game in a browser, probably outside any free Wi-Fi zone, with a not so high download speed. You simply can't make them wait half an hour just to download a song unless your name is Lady Gaga and that sound is your latest smash hit.
People want to press play and play your game; remember, you are making games, not sounds in a matter of seconds, so choose your sounds wisely, they can't be bigger than the game itself.
Play with sound quality until you find a good compromise between quality and weight, and when choosing background...