The speed of sound in a synthetic and a real distillation cut has been measured up to p = 150 MPa in the temperature range T = (293.15 to 373.15) K. The synthetic system, which is representative of distillation cuts, is made up of five components with high boiling point temperatures of about T-b = 523 K belonging to essential chemical families found in natural fluids {iso, or n-paraffins, naphthenes, and aromatics (alkybenzene, or alkylnaphtalene)}. The distillation cut comes from the separation of a standard crude oil by distillation around T = 523 K. The measurements allow the evaluation of various thermophysical properties such as densities, and isentropic and isothermal compressibilities up to p = 150 MPa with the help of additional density measurements performed at atmospheric pressure.