A boombox is a common term used for a portable cassette/CD player (the latter during the 1990s onward) and AM/FM radio with two sound amplifiers. They generally were the size of briefcases, unlike the more compact Walkman.
During the 1980s, both the Red Army and various Private Forces in Afghanistan and the Angola-Zaire border region of Africa, respectively, frequently utilized boom boxes to play various songs that were popular at the time. In addition, Quiet's cell on Mother Base contained a boombox that frequently played various songs. A Diamond Dogs soldier also carried a boombox around while celebrating the PF's commander, Venom Snake's birthday, in order to play their version of the tune "Happy Birthday."
In 2014, Outer Heaven's Haven Troopers utilized a boom box at a secluded cabin near the mountain trail in South America that played a facsimile of the then-captive Naomi Hunter's voice, as bait to draw out Solid Snake to kill him.
Behind the scenes
A boombox is an environmental object that first appears in Act 2, Solid Sun, of Metal Gear Solid 4: Guns of the Patriots, the sound of which is intended to mislead the player while tracking down Naomi Hunter in South America. Upon approaching the revealed boombox, the voice sample being played back will begin to loop indefinitely. If the player then shoots it, the sound will slow down and eventually cease.
Boomboxes frequently appear in Metal Gear Solid V: The Phantom Pain, which can be found in various enemy guard posts and bases, with each one playing back a specific audio track. Those that contain a collectible cassette tape result in the action button icon appearing on the game screen, when approached by the player character. After the cassette is removed, the audio track will cease and the boombox will fall over, with it remaining silent during later visits to the area. The collected cassette tapes can be listened to on the player character's Walkman, controlled with the iDroid. Other boomboxes play back faint though audible dialogue, although unlike those playing music, these can't be interacted with.
On the 26th of September, 2015, Berlin Boomboxes teamed up with KONAMI Europe to create a boombox as promotional material for MGSV: The Phantom Pain.