Ovation, a guitar manufacturer in Connecticut, is well-known for pioneering round-back acoustic/electric guitars. The company makes these guitars with a solid top and high-quality piezo-electric pickups but forgoes the traditional wooden back and sides. Instead, Ovation's acoustic/electrics have a rounded one-piece bowl molded out of a composite fiberglass. The purpose is to minimize the amount of feedback encountered by acoustic musicians playing through a P.A. system at full volume in large centers.
Reverb is the most common effect employed by acoustic guitar players when recording or playing through amplification. Electronically speaking, reverb refers to the practice of simulating the sound of an instrument when played in an acoustic chamber, where the original sound bounces back to the listener as it is reflected off of any hard surface. These could be the walls of a room, a hall or an auditorium. A bit of reverb adds a touch of warmth and realism to the sound of a guitar. Add more reverb and you can make the guitar sound distant through an amplifier or on a recording.
Feedback is still a frequent problem, despite the Ovation's rounded back and sides. When a guitar pumps a signal through a sound system, sometimes the guitar itself is affected by the vibrations produced by the sound system. A loud P.A. system or amplifier can cause a string to vibrate in sympathy with the P.A. signal. The P.A. system picks up the string vibrations and adds them to the signal, which makes the string vibrate in sympathy even more, strengthening the signal and creating a feedback loop. A "notch" is an effect that cuts the signal of a specific frequency. If a guitar has a tendency to feed back at 110 Hz, or an "A" note, the player can set the "notch" to this frequency, cutting the signal and breaking the feedback loop. Some Ovation guitars have built-in notch controls so the player can cut feedback without touching the sound system.
A delay effect is simply the storage and rebroadcast of a signal a split second to seconds later. You can set a delay to imitate a reverb effect, or you can use it to create a "slapback" effect or even more radical sounds. You can even use a delay to record and replay a loop of several seconds long and then play along with your own loop.
A chorus effect takes the incoming guitar signal and adds a slightly out-of-tune note to the signal to create a shimmering, otherworldly effect. The effect approximates the sound you get when multiple instruments are played together but are not quite perfectly in tune.