A tension adjustment hoop (1) for tensioning a resonant skin (13) on a musical instrument (6, 25), the tension adjustment hoop (1) being formed by a ring (2) with a centre axis (3) and with retention means (4) arranged to interact with coupling means (5) on the musical instrument (6, 25) for retention of the tension adjustment hoop (1), the tension adjustment hoop (1) having an opposing top side (7) and bottom side (8), where the tension adjustment hoop (1) comprises an inner fluid channel (17), provided with a pressure adjustment connection (26) in hydraulic connection with the fluid channel (17), and a plurality of pistons (10), each in hydraulic connection with the fluid channel (17), each with a free end (11) opposite the fluid channel (17), and each, under the influence of the pressure in the fluid channel (17), being displaceable in a direction parallel to the centre axis (3) of the tension adjustment hoop (1) between a first extreme position, where the free end (11) is within or level with the bottom side (8), and a second extreme position, where the free end (11) is outside the bottom side (8).