This is a Fictitious Artist.
The Seatbelts are a group of artists that came together to compose music for the soundtracks to Cowboy Bebop. The name is that of their fictional band that exists in the Cowboy Bebop universe; they derive their name "from how the performers wear seatbelts to be safe while they play hardcore jam sessions." In real life, The Seatbelts are led by Yoko Kanno and a core group of the artists that she regularly works with on soundtracks plus other artists that perform as guests on many of her compositions. The wiki and fan site relationships link to the list of the instruments the artists play for the main members.