A compensator for a tremolo for a stringed musical instrument, such as an electric guitar. The spacing between opposite groove walls of the groove is smaller than the leveled cover strip. A variable adjustment value is calculated, preferably at the central server, by comparing the predetermined amount already charged with the final transaction amount. The expansion side of the compressionexpansion unit in thermal contact with the heated cooling medium, which is at a first temperature level, so that heat is transferred from the heated cooling medium to the expansion side of the compressionexpansion unit. The scheduler determines a job workload for each of the physical resources, selects physical resources based on the job workload and selects a logical volume supported by the selected physical resources in a balanced manner. Each shroud is biased in the longitudinal direction to compress the packing seal by a plurality of spring stacks separated by a plurality of spacers.