Psychological Bulletin Copyright 1993 by the American Psychological Association, Inc. 1993. Vol. 113. No. 2. 345-361 0033-2909/93/53.00 Absolute Pitch Annie H. Takeuchi and Stewart H. Hulse Absolute pitch (AP) is the ability to identify a tone's pitch or to produce a tone at a particular pitch without the use of an external reference pitch. AP exists in varying degrees among people generally described as AP possessors. AP possessors vary not only in the accuracy with which they can identify pitches but also in their ability to produce pitches absolutely and in their ability to identify tones of various timbres and in various pitch registers. AP possessors' memory for pitches is mediated by verbal pitch names; they do not have superior memory for pitches per se. Although the etiology of AP is not yet completely understood, evidence points toward the early-learning theory. This theory states that AP can be learned by anyone during a limited period early in development, up to about age 6, after which a general developmental shift from perceiving individual features to perceiving relations among features makes AP difficult or impossible to acquire. Absolute pitch (AP) is the ability to identify the pitch of a work with units of a single tone, whereas composers without AP musical tone or to produce a musical tone at a given pitch must work with pitch relations that require a minimum unit of without the use of an external reference pitch. Most humans two tones. process musical pitch relatively rather than absolutely. They Psychologists have puzzled over several questions about AP process the melodic and harmonic relations among pitches in- for over 100 years. Why does AP occur so rarely? Does AP stead of the absolute pitches themselves. In contrast, people involve superior memory or superior discrimination of pitches? who have AP can encode and remember absolute pitches. Do AP possessors perceive music in the same way that nonpos- AP is a rare ability; its incidence is generally estimated at less sessors do? Is AP learned, and if so, how? Why is it learned by than .01% of the general population (Bachem, 1955; Profita & some people and not by others? We address these questions in Bidder, 1988). Those who have AP claim that identifying the latter parts of this article. However, we begin by addressing pitches absolutely is effortless and immediate (Bachem, 1940; a more basic question: What exactly can an AP possessor do? Corliss, 1973; Profita & Bidder, 1988; Revesz, 1953) and that they made no special effort to develop AP (Baird, 1917; Boggs, Abilities of AP Possessors 1907; Weinert, 1929, cited in Petran, 1932). In contrast, efforts by adults to develop AP have never achieved unqualified suc- Methods of Measuring AP cess, although efforts to teach children AP have been more successful. Three kinds of tasks have been used to measure AP: identifi- These characteristics of AP would not excite so much interest cation tasks, production tasks, and memory decay tasks. We were it not for the fact that AP is generally considered a desir- discuss each of these tasks in the following sections. able ability. AP is useful to musicians, especially when studying atonal music (Crutchfield, 1990). In atonal music, there is no Pitch Identification Task tonic pitch that can serve as a reference point. Therefore it is more difficult to detect minor pitch errors by determining The most common method of assessing AP is with a pitch pitch relations in atonal music than in tonal music. AP enables identification task. Subjects are asked to identify absolutely the a performer or listener to detect pitch errors on an absolute pitches of various tones. In Western music, the octave, which is basis, without having to determine pitch relations. In addition, the interval formed by two pitches whose fundamental fre- Abraham (1901, cited in Petran, 1932) suggested that AP could quencies stand in a 2:1 ratio, is divided into 12 parts. The divi- be an advantage to composers because it would enable them to sion is into logarithmically equal parts in the equal-tempered tuning system, the tuning system most commonly used in psy- chological studies. Theoretically, the frequency at each point of Annie H. Takeuchi and Stewart H. Hulse, Department of Psychol- division corresponds to a musical pitch, although in musical ogy, Johns Hopkins University. practice, a small range of frequencies surrounding the division We thank Robert Crowder and an anonymous reviewer for their is accepted as corresponding to a particular musical pitch. comments on a draft of this article. Preparation of this article was Thus, there is a many-to-one mapping of frequency to pitch in supported in part by National Science Foundation Research Grant BNS -8911046 to Stewart H. Hulse and by a National Science Founda- music. tion predoctoral fellowship awarded to Annie H. Takeuchi. Pitch names are composed of two parts. The first part is the Correspondence concerning this article should be addressed to An- pitch class, for example, C, C-sharp, or D. The frequency at each nie H. Takeuchi, who is now at the Research Laboratory of Electron- of the 12 divisions of an octave corresponds to a different pitch ics, Room 36-747, Massachusetts Institute of Technology, Cambridge, class. The distance from one pitch class to an adjacent pitch Massachusetts 02139. class is called a semitone. In an equal-tempered tuning system, 345 346 ANNIE H. TAKEUCHI AND STEWART H. HULSE tones a semitone apart have fundamental frequencies forming a would be perfect. Two bits of information implies 4 response 21/12:1 ratio. The second part of a pitch name is the octave categories would produce perfectly accurate identification; 3 designation. All pairs of tones an octave apart have the same bits implies 8 response categories, and so on (Miller, 1956). pitch class; they are distinguished by their octave designation. Measuring performance in terms of information transmitted Although there is no universal means of designating octaves in eliminates the need to establish criteria for a correct or incor- music, in the most commonly used system, the octave runs rect pitch identification because it measures consistency rather from C up to B, and middle C (261.6 Hz) is designated C4. The B than accuracy of identification. AP possessors can retain about next to middle C (246.9 Hz) is B3. The C an octave above middle 6 bits of information about pitch, which corresponds to about C (523.2 Hz) is C5, the C an octave below middle C (130.8 Hz) is 64 response categories (Attneave, 1959; Carroll, 1975; Ward, C3, and so on. The pitch A4, used to tune orchestras, corre- 1953, 1963b), whereas nonpossessors retain on average about sponds to 440.0 Hz by modern convention. 2.5 bits or 5.7 categories (Fulgosi, Knezovic, & Zarevski, 1984; Accuracy of absolute pitch identifications. Percentage of Hartman, 1954; Pollack, 1952,1953). correct identification is the most common measure of perfor- Given the foregoing, how accurate are absolute pitch identifi- mance in pitch identification tasks, and under normal circum- cations as measured by percentage of correct identification? In stances, the measure works well. However, simple percentage Table 1, we present the results of several absolute pitch identifi- correct can be a misleading index under certain conditions. cation experiments conducted since 1970. The table shows the Some subjects may consistently identify pitches a semitone low range and the mean of the percentage of correct pitch identifi- or a semitone high (Bartholomew, 1925, cited in Petran, 1932; cations by AP possessors in each experiment, where correct- Weinert, 1929, cited in Ward, 1963a). This can occur because a ness is determined by the criteria given in the rightmost col- subject is accustomed to a different tuning standard for A4 than umn. Octave errors, which are discussed below, occur when the 440.0 Hz. There are also anecdotal reports that as a result of pitch class of a tone is correctly identified but the octave identi- aging, an AP possessor's pitch perception may shift by one or fication is incorrect. two semitones, so that all pitch identifications are one or two It is apparent from the table that accuracy of absolute pitch semitones too high (Triepel, 1934, cited in Ward & Burns, 1982; identification has varied widely across experiments. There are a Vernon, 1977). To the extent that pitch perception depends on number of possible reasons for this fact. One is that experi- the place of maximum stimulation on the basilar membrane, menters have used different methods to determine whether a this shift in absolute pitch perception may be due to loss of particular subject would qualify as an AP possessor. For exam- elasticity of the basilar membrane as the subject ages, which ple, Zatorre and Beckett (1989) relied on self-reports. In con- results in a gradual shift in the place where a particular fre- trast, Miyazaki (1988a) simply tested a number of music stu- quency maximally excites the basilar membrane (Vernon, 1977; dents and determined from analysis of the data which subjects Ward & Burns, 1982). were AP possessors. Other factors affecting accuracy of identi- Ward (1963a, Ward & Burns, 1982) proposed four solutions to fication, which are discussed in more detail later, are the timbre the problem of measuring AP in subjects who consistently err and pitch register of the tones tested. Also, it has been widely by a semitone. The first solution was to adjust the stimuli to reported that tones above 4000-5000 Hz lose their musical each individual subject's musical scale, which would involve a quality and have no distinct pitch class (Semal & Demany, 1990; calibration process before actually testing absolute pitch identi- Stevens & Volkmann, 1940; Ward, 1954).