We might begin by asking how listeners know what schema to start with. We already know that an isolated tone tends to be heard by listeners as the tonic. But is this the tonic of a major or minor key? Following exposure to an isolated 2-second tone, listeners are more than three times as likely to expect a tone whose pitch is a major third above as a minor third
above. This implies that Western listeners have a tendency to start by assuming a major mode. [4] It is conceivable that a musically-pertinent schema may be invoked prior to the onset of any sound.
Once the music has begun, how fast are listeners able to recognize the musical context? In the case of music, dramatic changes in listeners' expectations arise depending on the style or genre of the music. Perrott and Gjerdingen (1999) have observed that listeners are very quick to
identify different styles. When scanning the radio dial, listeners make split-second decisions regarding the style of music being played on each station. Perrott and Gjerdingen tested this observation by selecting
random musical segments from samples of 10 different styles of music, including jazz, rock, blues, country & western, classical, etc. They showed that listeners are adept at classifying the type of music in just 250
milliseconds. With just one second of exposure, ordinary listeners' abilities to recognize broad stylistic categories is nearly at ceiling; that is, further exposure to the musical work does not lead to a significant improvement in style identification. If we assume that identifying a schema is
tantamount to activating the schema, then these observations suggest that experienced listeners can activate a schema appropriate to the genre of music they are hearing in a very short period of time.
What about the phenomenon of schema switching? How rapidly can a listener switch from one schema to another? Although little research has been carried out pertaining to this question, suggestive evidence has come from the work of Krumhansl and Kessler (1982). Krumhansl and Kessler traced the speed with which a new key was established in modulating chord sequences. Modulations to related keys were "firmly established" within three chords lasting a few seconds (Krumhansl, 1990; p.221). However, some sense of the initial key was maintained throughout the modulating passage. Since modulation is common in Western music, this ability to switch rapidly between schemas might pertain only to
key-related schemas. One might imagine that switching, say, from a Western string quartet to Beijing opera would take longer -- although perhaps not very long in absolute duration. Bi-lingual speakers differ in their abilities to switch rapidly between different languages. But this skill appears to be related to how often speakers must change language in their daily life.
What cues signal the listener to switch schemas? Two plausible sources of cues for schema switching can be identified: auditory and non-auditory. One source might be obvious and persistent failures of expectation. Once again, switching between two languages is instructive. If a person has been conversing in French, then the failure of an utterance to conform to the schematic expectations for French ought to lead to a re-evaluation of the language context, and so precipitate switching to a different language schema. Similarly, the failure of pitch-, rhythm-, timbre- or other related expectations might be expected to instigate a search for a more
A second source of pertinent cues can be found externally to the sounds themselves. For example, seeing five brass players on a concert stage will already evoke certain associations and expectations. If the players were dressed in dark evening suits, even more specific expectations might arise. Conversely, if the players were dressed in military uniforms, or if the players were dressed informally and standing on a New Orleans street, the expectations would differ. There are innumerable visual and other
environmental cues that presumably pre-dispose the listener to invoke a particular musical schema.
The auditory and non-auditory cues the provoke schema switching might also provide plausible cues through which new schemas are created. The persistent failure of expectations might well raise the alarm that a novel cognitive environment has been encountered and that the listener's existing pallet of schemas is inadequate. An interesting consequence of this view is that it should be difficult to form a new schema when the new context differs only slight from an already established schema. Once
again, language provides a useful analogy. Native English speakers who learn a latinate language, often encounter difficulty learning a second latinate language. For example, a non-fluent knowledge of Spanish may interfere with the ability to learn Italian. Italian vocabulary and grammar may begin to interfere retroactively with one's Spanish abilities. The
difficulty appears to be the failure, from an English speaker's perspective, to sufficiently distinguish Italian from Spanish. This confusion appears to be reflected in neurological studies. It is often the case that cortical areas associated with a native language are segregated from cortical areas associated with an acquired second language. However, a third acquired language will often share cortical regions associated with the second acquired language. In this case, the weak cognitive barrier between schemas is reflected in an apparently weak neurophysiological barrier. Whatever form these barriers take, they are clearly important in order to maintain the modular structure of auditory schemas. As we noted earlier, these cognitive barriers allow a listener to be surprised by events that in one schema are common, but in another schema are uncommon. While a modern listener might be quite familiar with jazz, this same listener might well find a moment of syncopation in a Renaissance motet to be somewhat "shocking." Such experiences imply that relatively strong barriers exist between schemas. Indeed, in Castellano, Bharucha and Krumhansl (1984) it was found that American listeners did not carry over Western pitch
this]. More research is clearly needed to determine the extent to which one musical schema can influence another.