Stef Bruinsma, also known as Cooly D, is a Dutch rapper, music producer and studio engineer born and raised in Enschede. He began his career as a solo artist but found his true calling by founding the hip-hop group Flip Da Scrip with rapper Glaze. With their 1993 debut album Products Of Da Piemel, the group established itself in the Dutch hip-hop scene, backed by club shows and TV appearances on shows hosted by Jos Brink and Telekids. The singles "Who's In Da House" and "Throw Ya Hands In The Air" reached the Tipparade in 1994 and 1995.

Cooly D also co-hosted the weekly hip-hop show The Pitch on TMF with Glaze. The group had big success in Germany, signing with the Dos Or Die label and performing for tens of thousands at Borussia Dortmund's stadium and at events like the Dome Festival in Cologne.

When Glaze went solo in 1997, Stef continued the group with rapper Bear and singers Winston and Crucial. The single "I Never Told You" reached #32 in the Dutch Top 40 and earned gold records in Hungary through the collaboration with Dos Or Die and Sony.

Alongside Flip Da Scrip, Stef built an impressive career as a studio engineer and producer. He started at Future Sound Studios, working on productions and remixes for artists like Quincy Lizer, Skeelo, La Toya Jackson and Michelé. In 1990 he spent time in Los Angeles with DJ Flash and King MC on West Coast underground projects for Priority Records. Meeting Steve Clisby in 1991 proved crucial: Clisby taught him the ins and outs of production and inspired him to open his own studio in Enschede.

In 2017 he launched Stefario, his name as an all-round producer with a focus on dancehall. As Stefario he produced singles for dancehall artists such as Shockman and Big Shenn, including the dancehall hit "Wine Deh", and worked with names like Beenie Man on "Bring It". His Stefario productions have since passed millions of streams on Spotify.

Two names, one sound: from Dutch hip-hop in the '90s to dancehall today, his career blends his own artistic achievements with contributions to the careers of others, and his work still resonates in the Netherlands and abroad.