Snake's iPod can download specific tunes throughout the course of the game. Some songs have an additional "secret" effect when it is played in the game.

Beyond the Bounds - Stage 4 Shadow Moses, Tank Hangar. After power is restored, backtrack to the upper catwalk and explore all rooms. When played, this tune increases stun damage done by Snake from non-lethal weapons.

Big Boss - Earn the Big Boss emblem (see another code on this page for the criteria). This tune will increase stun damage (as above) and increases Snake's accuracy when played.

Bio-hazard - Stage 3 Europe, Midtown. Hold-up a resistance soldier and perform a body search. This tune will cause soldiers held by Snake to scream in terror.

Destiny's Call - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to go enraged.

Flowing Destiny - Stage 4 Shadow Moses, Canyon. Before leaving the canyon area, examine the rocky walls for a hole hiding this item. This tune will cause soldiers held by Snake to weep like a little girl.

Fury, The - Stage 2 South America, Cove Valley Village. Inside the fire ravaged house. This tune will cause soldiers held by Snake to go enraged.

MGS 4 Love Theme / Action - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to weep like a little girl.

Opening - Old L.A. 2040 - Stage 4 Shadow Moses, Nuclear Warhead Storage B2. Input 78925 into Otacon's lab computer. This tune will increase Snake's accuracy.

Policenaughts Ending - Stage 4 Shadow Moses, Nuclear Warhead Storage B2. Input 13462 into Otacon's lab computer. This tune will cause soldiers held by Snake to fall asleep on touch.

Rock Me - Stage 2 South America, Confinement Facility. Island in the south-eastern quadrant. This tune increases Snake's amount of life recovered from items and other means.

Sailor - Stage 2 South America, Vista Mansion. Between the east wall and a cargo container. This tune increases Snake's amount of life recovered from items and other means.

Show Time - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to scream in terror.

Snake Eater - Unlocked by earning all 40 game clear emblems. This tune will increase the life recovery rate of Snake through items and other actions.

Subsistence - Play at least one game of Metal Gear Online. You must start the match with at least two players (and not simply wander around alone or on the Training Servers). This tune will increase Snake's accuracy.