Not much is extant, so we rely considerably on images and writings. For secular music, you would would play whatever you had (vs. the "consorts" of the renaissance), supplying a drone or a doubling of the voices, maybe elaborating the voice line, or playing textless instrumental dance pieces such as the istampita, or estampie (which typically had puncta, what we would call first and second endings). "Haut" referred to "high," but really loud, outdoor instruments. "Bas" referred to "low," but really softer, indoor instruments.
The ancient Greeks used the hydraulis -- a water-powered organ -- for entertainment. (And in this capacity the organ survives into the 20th century for silent movies and to today at baseball games.) But the pagan and fun associations retarded its use for the medieval church. Evidence appears only beginning in the 9th century that the organ was used in church. Available was the portative organ which would be pumped with one hand and played with the other (with the range between one and two and a half octaves), and the late medieval positive organ, which another person would pump. The organ had no stops at this time.
More typical of secular music was, among the stringed instruments, the harp, the lute (plucked), the vielle (bowed, a proto-violin with a fifth string serving as a drone), the rebec (bowed, pear-shaped and producing a nasal sound), and the psaltery (plucked with fingers or quills). Among the winds were the reed instruments -- the shawm (double reed) and the aulos -- recorders and flutes (including panpipes), and fairly crude trumpets. Percussion included the small tabor, timbrels, tambourines, bells and assorted drums.