Without even looking, there are are handful of easily identifiable sounds: Mario jumping, Sonic losing coins, and PacMan skirting around a maze, just to name a few. But one we've most recently become familiar with is Apple's "tri-tone" alert—Boo-Dah-Ling—which first hit the scene when the original iPhone was released in 2007. Surprisingly, however, that simple tune wasn't even meant for Apple's smartphone, but an early MP3 player on the Mac called SoundJam MP.
In a fun origin story post, Kelly Jacklin, software engineer and media producer, explains how he was tasked with creating a sound for SoundJam MP that would tell people the program was finished burning a CD. Jacklin says he wanted to make something simple, something without clutter, a sound that would grab someone's attention. And after some experimentation with Mac's Common Lisp program, Jacklin came up with a short and happy 3-note sequence that's now a huge part of the iOS platform.
SoundJam MP was eventually acquired by Apple as the building blocks for iTunes—afterwards, Jacklin's short melody made it onto the iPhone, and the rest is history. Of course, Jacklin's tri-tone alert is used elsewhere in Apple's ecosystem, including once a CD is done burning in iTunes. Things did eventually come full circle for the catchy sound, but it's neat to hear how the alert was intended for something else all along, yet it's one of the most recognizable sounds today.
For Jacklin's full story, hit up his blog at the source link below, including how and why he created the sound in the first place.