A tonearm is an important part of a turntable that supports the cartridge and stylus as they track the grooves of a vinyl record. Its job is to allow the stylus to follow the record accurately while minimising unwanted movement and vibration.

The cartridge is mounted at the end of the tonearm, usually in a headshell or directly onto the arm. The stylus extends from the cartridge and sits within the record groove. As the record rotates, the tonearm gradually moves towards the centre of the record while allowing the stylus to follow the groove.

At the opposite end of many tonearms is a counterweight. This is used to balance the arm and set the correct tracking force, which determines how much downward pressure the stylus applies to the record. Cartridge manufacturers normally specify a recommended tracking force for their cartridges.

Many tonearms also include an anti-skate adjustment. As a record plays, forces acting on a pivoted tonearm can tend to pull it towards the centre of the record. Anti-skate applies a compensating force to help the stylus track the groove correctly.

Tonearms are available in several different designs. The most common are pivoted tonearms, which rotate around a fixed point. These can be straight or curved and include designs such as S-shaped arms. Linear-tracking tonearms operate differently by moving the cartridge across the record in a straight line.

The materials used to construct a tonearm can include aluminium, carbon fibre and other lightweight, rigid materials. The arm needs to be sufficiently rigid to support the cartridge accurately while controlling unwanted resonances that could interfere with playback.

Tonearm and cartridge compatibility is also important. The effective mass of the tonearm and the compliance of the cartridge suspension influence how the two components behave together. A suitable combination helps the cartridge track the record correctly.

Some tonearms also allow adjustments such as arm height, vertical tracking angle and azimuth. These settings can help position the cartridge and stylus correctly in relation to the record surface.

The tonearm therefore does considerably more than simply hold the cartridge above the record. By controlling the position, movement and tracking force of the cartridge, it plays an important role in allowing the stylus to retrieve the information contained within a vinyl record's grooves.