This is the first title in the Hard Truck series not to be developed by SoftLab-Nsk. ValuSoft licensed the name Hard Truck for a Wheels of Steel series, and this game has an entirely new codebase.
You can put your custom music into "...\game\usr\music\jukebox" folder. file format can be in standard uncompressed Windows ".WAV" format or in compressed Ogg Vorbis ".OGG" format. Custom music will be playing in the jukebox ("J" key by default).