The ability to play two notes at once. Some dual-oscillator mono-synths allow the keyboard to generate two control voltages (from the lowest and highest keys played) which are routed to separate oscillators allowing two notes to be played simultaneously (see Paraphonic). For example, the ARP Odyssey and the Moog Subsequent are both duophonic synths.

In the context of musical instruments, the term polyphonic refers to the number of notes that an instrument can play simultaneously. Most poly-synths can play up to 6 or 8 notes at a time, some 16 or 32, and others many more depending on the technology involved.

Advanced Tranmission Line — a term coined by PMC Loudspeakers to describe the specific vented-cabinet design employed in all of their loudspeakers. (See Bass Reflex and Transmission-Line)

See Bass Reflex

A bass reflex loudspeaker employs a cabinet with a vent (or port) which allows some of the energy from the rear of the driver unit's diaphgram to supplement that from the front at low frequencies, improving the overall efficiency and allow a greater bass extension (but with a steeper roll-off) for a given size of cabinet.