| Artiest / Band   | Titel | |
|---|---|---|
|   | OBERON (2014) | DREAM AWAKENING | 
|   | OBERON (2021) | A MIDSUMMER'S NIGHT DREAM (1970), heruitgave | 
|   | OBRAZTSOFF, ALEXEY (2012) | BEATOOM (NL+E) | 
|   | OCEANS OF NIGHT (2009) | THE SHADOWHEART MIRROR | 
|   | OCEANS OF NIGHT (2011) | DOMAIN | 
|   | OCEANS OF NIGHT (2014) | MIDNIGHT RISING | 
|   | OCTARINE SKY (2021) | CLOSE TO NEARBY | 
|   | ODIN'S COURT (2015) | TURTLES ALL THE WAY DOWN | 
|   | ODIN'S COURT (2016) | DEATHANITY (R3) (2008), heruitgave | 
|   | ODYSSICE (2016) | MOONDRIVE PLUS (1997), heruitgave | 
|   | OJEDA, EDDIE (2005) | AXES 2 AXES | 
|   | OLYAM (2013) | ORANGE LOVE (NL+E) | 
|   | OLZON, ANETTE (2014) | SHINE | 
|   | OMNI (2003) | OMNI (NL+E) | 
|  | OMNIA (2003) | HORMONAL | 
|   | OOSTEN, MANNY VAN (2005) | INFERNORAMA: A SYMPHONY FOR THE HEARTLESS | 
|   | OPERA TO RELAX (2005) | BETWEEN TOMORROW (NL+E) | 
|   | OPERATION: MINDCRIME (2015) | THE KEY | 
|   | OPERATION: MINDCRIME (2016) | RESURRECTION | 
|   | OPEROSE (2020) | OCEANS OF STARLIGHT | 
|   | OPPOSING MOTION (2013) | LAWS OF MOTION | 
|   | ORPHAN AMPS (2012) | UNEXPECTED MEMORIES | 
|   | ORPHAN PROJECT (2003) | ORPHAN FOUND | 
|   | ORPHAN PROJECT (2008) | ORPHAN PROJECT II | 
|   | ORPHANED BEE, THE (2025) | THINKING WITHOUT LANGUAGE | 
|   | ORPHEO (2003) | SONGS OF PAST DAYS TO COME | 
|   | ORPHEO (2005) | ECHOES (E) | 
|   | OSADA VIDA (2008) | THE BODY PARTS PARTY | 
|   | OSADA VIDA (2012) | WHERE THE DEVILS LIVE | 
|   | OSADA VIDA (2013) | PARTICLES | 
|   | OSADA VIDA (2016) | UNINVITED DREAMS | 
|   | OSANNA & DAVID JACKSON (2013) | PROG FAMILY | 
|   | OTR (2008) | MAMONAMA | 
|   | OUT OF FOCUS (2010) | WAKE UP (1970), heruitgave | 
|   | OUT OF FOCUS (2011) | FOUR LETTER MONDAY AFTERNOON (1972), heruitgave | 
|   | OUT OF FOCUS (2011) | OUT OF FOCUS (1971), heruitgave |