2/13 -- We just spoke to Mystikal, and he tells us he's grateful for the opportunity to get back to being a father and creating music. He says being on the outside again is a surreal feeling.

The rapper tells us he spent a lot of his time behind bars writing memoirs and music, and fine-tuning songs he had written before but never released.

Mystikal's getting a taste of freedom ... after spending 18 months behind bars on rape charges, he's finally posted a very hefty bond ... TMZ has learned.

Mystikal's attorneys tell us the rapper was able to scrape together $3 million for the bond ... securing his release from a Louisiana prison. We're told the money came from an advance for a new recording deal, and funds raised by Mystikal's family and friend.

TMZ broke the story ... Mystikal -- real name Michael Tyler -- was ironing out the final details last month. He'd been behind bars since August 2017 when he was booked for first-degree rape and second-degree kidnapping.

Mystikal's attorney, Tim Yazbeck, tells TMZ ... "It's been a long time coming for Mike, but now he can get back to being the artist he is, doing what he loves, and seeing his kids again."

The rapper's now free until his pending trial in May.

Mystikal's other legal eagle, Joel Pearce, tells TMZ ... they're confident in their case. Pearce said, "Based on all of the evidence we have, we strongly believe that an amicable resolution is not only possible but probable as an outcome in this case and that Michael Tyler will never be made to return to jail for a crime he didn't commit."