The 17-track project, dubbed San Quentin Mixtape, Vol. 1., is dropping Friday, and Kim surprised David with this congratulatory message ... admiring his work, passion and dedication to his music-led prison initiative.

David, an award-winning producer who wrote and produced for Britney Spears, Sean Kingston, and Ashley Tisdale before being incarcerated, is the mixtape's brainchild ... he used a keyboard to makes beats in his San Quentin cell, and had other inmates rap about their stories.

Along the way, David's vision captured the hearts and minds of a host of celebs ... with Kim, J. Cole, MC Hammer and Common among the famous folks who visited San Quentin to see what Jassy was cooking up, and encourage the inmates to keep doing their thing.

David spent 11 years in San Quentin as part of his sentence for killing a man during an altercation, but while inside ... he worked with the prison to establish a music-focused initiative within the Youthful Offenders Program. He taught inmates how to write, produce and record their own music in a studio.

Jassy used his contacts in the music industry and other donors to support the program with enough donated audio equipment to build a full-scale production studio inside the prison's media lab.

The end result -- a project delving into the life experiences of 17 different inmates, exploring their struggles behind bars while encouraging the next generation to learn from their mistakes and forge a better path.

Kim says David and the 17 inmates featured on the mixtape should be very proud of themselves, and she can't wait for the world to hear their positive message -- the mixtape has no profanity.