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.

Tune	How to unlock
Beyond the Bounds (increases stun damage done by Snake from non-lethal weapons)	Stage 4 Shadow Moses, Tank Hangar. After power is restored, backtrack to the upper catwalk and explore all rooms
Big Boss (increase stun damage and increases Snake's accuracy when played)	Earn the Big Boss emblem
Bio-hazard (cause soldiers held by Snake to scream in terror)	Stage 3 Europe, Midtown
Boktai 2 Theme	At the Act 2 mission briefing, go upstairs in the Nomad.
Bon Dance	At Act 2 in the Marketplace.
Destiny's Call (cause soldiers held by Snake to go enraged)	A random gift from a militia or rebel soldier if Snake gives them a healing item
Flowing Destiny (cause soldiers held by Snake to weep like a little girl)	Stage 4 Shadow Moses, Canyon. Before leaving the canyon area, examine the rocky walls for a hole hiding this item
Fury, The (cause soldiers held by Snake to go enraged)	Stage 2 South America, Cove Valley Village. Inside the fire ravaged house
Inorino Uta	At the Act 1 mission briefing.
Level 3 Warning	At Act 1, Advent Palace.
Lunar Knights Main Theme	At the Act 4 mission briefing, upstairs in the Nomad.
Metal Gear 20 Years History	Part 2: At Act 4, in Warhead Storage Building B2.
Metal Gear 20 Years History	Part 3: At Act 2, at the South America Confinement Facility in the room with beds inside the house.
Metal Gear Solid Main Theme (The Document Remix)	At Act 5, under the hatch to the left at the start of the area.
MGS 4 Love Theme / Action (cause soldiers held by Snake to weep like a little girl)	A random gift from a militia or rebel soldier if Snake gives them a healing item
On Alert	At Act 3, Midtown N Sector.
One Night in Neo Kobe City	At Act 3, Midtown, hold-up a PMC soldier.
Opening - Old L.A. 2040 (increase Snake's accuracy)	Stage 4 Shadow Moses, Nuclear Warhead Storage B2. Input 78925 into Otacon's lab computer
Policenaughts Ending (cause soldiers held by Snake to fall asleep on touch)	Stage 4 Shadow Moses, Nuclear Warhead Storage B2. Input 13462 into Otacon's lab computer
Rock Me (increases Snake's amount of life recovered from items and other means)	Stage 2 South America, Confinement Facility. Island in the south-eastern quadrant
Sailor (increases Snake's amount of life recovered from items and other means)	Stage 2 South America, Vista Mansion. Between the east wall and a cargo container
Shin Bokura no Taiyou Theme	At the Act 3 mission briefing, upstairs in the Nomad.
Show Time (cause soldiers held by Snake to scream in terror)	A random gift from a militia or rebel soldier if Snake gives them a healing item
Snake Eater (increase the life recovery rate of Snake through items and other actions)	Unlocked by earning all 40 game clear emblems
Subsistence (increase Snake's accuracy)	Play at least one game of Metal Gear Online. You must start the match with at least two players
Test Subject's Duality	At Act 3, Midtown S Sector.
The Best Is Yet To Come	At Act 4, Snow Field just before the "Disc Change" Codec transmission.
The Essence of Vince	At Act 3, Echo's Beacon.
The Fury	At Act 2, in the Cave Valley Village in the badly burned building.
The Fury	At Act 2: South America, Cove Valley Village, search inside the fire-ravaged house. This song causes soldiers held by Snake to become enraged.
Theme of Solid Snake	At Act 1, Millennium Park.
Theme Of Tara	At Act 1, Militia Safehouse, just before seeing the unmanned flying-bomber on the table.
Warhead Storage	At Act 4, Tank Hanger, upper floor ventilation shaft.
Yell (Dead Cell)	At Act 4, Casting Facility North.
Zanzibarland Breeze	At Act 1, Urban Ruins before intermission sequences.