The portion of a synthesizer where most or all of the controls and displays are mounted. On most synths, it serves as the primary user interface for operating, patch editing, and general control of the synth for all purposes other than actually playing notes. The front panel will nearly always be painted with graphics which label the function of each control, as well as index scales (the little marks around a control that let you visually reference the setting of the control) and possibly line graphics that illustrate routing or other information. On synths with one-knob interfaces, the front panel sometimes contains a printed legend that associates parameters with displayed parameter numbers. Common background colors for synth front panels are black and dark gray, although other colors are used.
On a rackmount synth, the front panel also serves as the structural interface to the rack rails. All of the rest of the synth, including the case and all of the internals, mounts to the front panel, which in turn mounts to the rack rails. (This is true of all 19" rack mount gear, not just synths.) Because of this, the front panel must be very strong. Rack mount front panels are usually made of thicker aluminum for this reason.
On a modular synthesizer, the front panel, in addition to containing all controls and displays, also contains the module's I/O jacks. The panel must be sturdy to withstand the forces of plugs being inserted into and removed from the jacks. Modular-synth modules are open on all sides except the front; they rely on the case they are mounted in for enclosure. So all of the electronics have to be attached to or suspended from the front panel in some fashion. A common method of attaching circuit boards to the panel is to rely on potentiometers for structural connection; the pots are soldered to the circuit board and then mounted via threaded nuts to the panel. Most modular synth front panels are made from thick sheet aluminum, although other materials such as Lucite/Perspex and fiberglass circuit board substrate are sometimes used. DIY'ers use a variety of means to add graphics to their panels; Dymo embossed labels were once common although they tend to fall off after a while. Laser printed graphics are common now, as well as a variety of iron-on transfer methods. A company named Schaeffer is popular in the DIY community for fabricating one-off and short-run panels.