You can easily add your own music to the game.
Just drag & drop your .mp3-files in the designated folder in the game directory.

Example: D:\Programme\Steam\steamapps\common\MGS_TPP\CustomSoundtrack

In this folder should already be the track 'Sands', in case if you're wondering why it's there.
Adding folders there only changes the order of the tracks ingame, corresponding to their names.

• Cat's in the Cradle - Harry Chapin

• Killer Queen - Queen

• Fox On The Run - Sweet

• The Ballroom Blitz - Sweet

• How Deep Is Your Love - Bee Gees

• Stayin' Alive - Bee Gees

• Don't Bring Me Down - Electric Light Orchestra

• On The Radio - Donna Summer

• Another One Bites The Dust - Queen

• Back In Black - AC/DC

• Breathing - Kate Bush

• Fade To Grey - Visage

• Hells Bells - AC/DC

• Cambodia - Kim Wilde

• Demolition Man - Grace Jones

• Me! I Disconnect From You - Grace Jones

• Walking In The Rain - Grace Jones

• Africa - Toto
recommended by Quinneth

• Beat It - Michael Jackson

• Let Me Go - Heaven 17

• Lightning Strikes - Aerosmith

• Love Is A Battlefield - Pat Benatar

• Mad World - Tears for Fears

• Maniac - Michael Sembello

• Somebody's Watching Me - Rockwell

• Temptation - Heaven 17

• That’s All - Genesis

• Think of Laura - Christopher Cross

• Time After Time - Cyndi Lauper

• What A Feeling - Irene Cara

• Against All Odds - Phil Collins

• All Cried Out - Alison Moyet

• Almost Paradise - Mike Reno and Ann Wilson

• Eyes Without a Face - Billy Idol

• Forever Young - Alphaville

• Is This The World We Created...? - Queen

• I Want To Know What Love Is - Foreigner

• Like A Virgin - Madonna

• People Are People - Depeche Mode
recommended by TTV | PapaBacon98

• Pride (In The Name Of Love) - U2

• Purple Rain - Prince

• Self Control - Laura Branigan

• Such A Shame - Talk Talk

• What's Love Got To Do With It - Tina Turner

• Wild Boys - Duran Duran

I made this 'guide' only for sharing tracks that suit the game taking place in the year 1984.
Of course you can add whatever music you want. Maybe I'll add some more tracks in the future.