Progressive music shunned the traditional structural notions of popular music. Rather than simple verse and chorus forms, progressive songs used extensive musical interludes and sections concentrating more on a change of dynamics (volume) or key. Forms of classical music were often present, blending the tradition of solos with jazz concepts of improvisation. This often stretched songs to well over 20 minutes long.
Progressive rock bands avoided the straight rhythms found in pop music. They would often use complex time signatures more akin to jazz . Due to the often improvisational style of bands such as Yes, the rhythm remained loose and free to allow the soloist more room to play. Quick changes in tempo are also a common recurrence.
Unlike pop music, progressive rock does not stick to one particular signature melody for a song. It tends to use the classical concept of theme and variation whereby one or two melodic ideas are returned to and developed in different ways. The melodies are likely to be constructed from a modal arrangement rather than the pentatonic melodies found in rock and pop. Instead of conventional chords, diminished and augmented chords that jazz musicians use are found in prog rock.
Progressive rock bands also took a novel take on what an album should be. Concept albums were a collection of songs with a single idea that unified the various album's tracks. During progressive rock's heyday in the '70s, albums such as Pink Floyd's "The Wall" were created not as an unconnected collection of songs but as one evolving idea that followed a single narrative story.
As the name suggests progressive rock pushed the boundaries of how we looked at music and how music was made. This manifested itself not only in the music but also in the increasingly elaborate stage performances of prog bands. New instruments like synthesizers and sequencers were frequently used. For the first time large lasers and mirrors were synchronized with the music to make light and visual effects part of the live music experience.