Melodic fission explained

In music cognition, melodic fission (also known as melodic or auditory streaming, or stream segregation), is a phenomenon in which one line of pitches (an auditory stream) is heard as two or more separate melodic lines. This occurs when a phrase contains groups of pitches at two or more distinct registers or with two or more distinct timbres.

The term appears to stem from a 1973 paper by W. J. Dowling.^[1] In music analysis and, more specifically, in Schenkerian analysis, the phenomenon is often termed compound melody.^[2]

In psychophysics, auditory scene analysis is the process by which the brain separates and organizes sounds into perceptually distinct groups, known as auditory streams.

The counterpart to melodic fission is melodic fusion.^[3]

Contributing factors

Register

Listeners tend to perceive fast melodic sequences which contain tones from two different registers as two melodic lines.^[4] The greater the distance between groups of tones in a melody, the more likely they will be heard as two different and interrupted streams instead of one continuous stream.^{[5] [6]} Studies involving the interleaving of two melodies have found that the closer the melodies are in register, the more difficult it is for listeners to perceptually separate the melodies.^[7] Tempo is important, as the threshold for registrar distance between melodic phrases still perceived as one stream increases as the tempo of the melody decreases.^[8]

Timbre

The more distinct the timbre of groups of pitches within one stream, the greater the likelihood that listeners will separate them into different streams.^[9] Similar to results found with experiments in pitch level, slower tempos increase the chance of perception of timbrally distinct pitches as one continuous stream.^[10] Timbral difference may override registral similarity in the perception of segregated streams.^[11] Additionally, quick and contrasting attack times in groups of tones lead to fission.^[12]

Volume

Differences in volume of groups of pitches can also lead to stream segregation.^[13] Logically, the louder the volume of a group of tones, the greater likelihood of melodic fission. In addition, when two streams are perceptually segregated due to differences in volume, the quieter stream is perceived as continuous, but interrupted by the louder stream.^[14]

Repetition

Perception of separate streams builds as the melodic sequence is repeated over time, first rapidly, and then at a decreased rate.^[15] However, a few factors can impede this process and "reset" fission perception, including silence between presentation of the melody,^[16] alteration of signal location (right or left ear) of the melody, and abrupt changes in volume.^{[17] [18] [19]}

See also

• Counterpoint
• Countermelody
• Klangfarbenmelodie

Notes and References

1. W. J. Dowling (1973), "The perception of interleaved melodies", Cognitive Psychology 5, pp. 322-337. A. S. Bregman & J. Campbell (1971), "Primary auditory stream segregation and perception of order in rapid sequences of tones", Journal of Experimental Psychology 89, pp. 244-249, had spoken of "auditory stream segregation".
2. The term appears to have been coined by Walter Piston (1947), Counterpoint, New York, Norton, under the form "compound melodic line" (London edition, 1947, p. 23). In the context of Schenkerian analysis, see for instance Forte & Gilbert (1982), Introduction to Schenkerian Analysis, Chapter 3, pp. 67-80. See also Schenkerian analysis. Manfred Bukofzer (1947), Music in the Baroque Era, New York, Norton, had spoken of "implied polyphony".
3. Saighoe, Francis. "Resultant Melodies: A Psycho-Structural Analysis". Journal of the Ghana Teacher's Association, 1991, Vol. 1, pp. 30-39.
4. Book: Deutsch, Diana . Psychology of Music . . St. Louis, Missouri . 2012 .
5. Dowling, W. J. "The Perception of Interleaved Melodies". Cognitive Psychology, 1973, Vol. 5, 322-337.
6. Dowling, W.J., Lung, K.M., and Herrbold, S., "Aiming Attention in Pitch and Time in the Perception of Interleaved Melodies". Perception & Psychophysics, 1987, Vol. 41, 642-656
7. Bey, C, and McAdams, S. "Postrecognition of Interleaved Melodies as an Indirect Measure of Auditory Stream Formation". Journal of Experimental Psychology: Human Perception and Performance, 2003, Vol. 29, 267-279.
8. Book: Van Noorden, Leo . Temporal Coherence in the Perception of Tone Sequences . . The Netherlands . 1975 .
9. Wessel. David. Timbre Space as a Musical Control Structure. Computer Music Journal. 1979. 3. 45–52. 10.2307/3680283.
10. Warren. R. M.. Obusek, C. J. . Farmer, R. M. . Warren, R. P. . Auditory Sequence: Confusion of Patterns Other than Speech or Music. Science. 1969. 164. 586–587. 10.1126/science.164.3879.586.
11. Book: Deutsch, Diana . Psychology of Music . . St. Louis, Missouri . 2012 .
12. Iverson. P.. Auditory Stream Segregation by Music Timbre: Effects of Static and Dynamic Acoustic Attributes. Journal of Experimental Psychology: Human Perception and Performance. 1995. 21. 751–763. 10.1037/0096-1523.21.4.751.
13. Dowling, W. J. "The Perception of Interleaved Melodies". Cognitive Psychology, 1973, Vol. 5, 322-337.
14. Book: Van Noorden, Leon . Temporal Coherence in the Perception of Tone Sequences . . The Netherlands . 1975 .
15. Anstis. S. M.. Saida, S.. Adaptation to Auditory Streaming of Frequency Modulated Tones. Journal of Experimental Psychology: Human Perception and Performance. 1985. 11. 257–271. 10.1037/0096-1523.11.3.257.
16. Beavois. M. W.. Meddis, R.. Time Decay of Auditory Stream Biasing. Perception & Psychophysics. 1997. 59. 81–86. 10.3758/bf03206850. free.
17. Anstis. S. M.. Saida, S.. Adaptation to Auditory Streaming of Frequency Modulated Tones. Journal of Experimental Psychology: Human Perception and Performance. 1985. 11. 257–271. 10.1037/0096-1523.11.3.257.
18. Rogers. W. L.. Bregman, A. S.. An Experimental Evaluation of Three Theories of Auditory Scene Analysis. Perception & Psychophysics. 1993. 53. 179–189. 10.3758/bf03211728. free.
19. Rogers. W. L.. Bregman, A. S.. Culmulation of the Tendency to Segregate Auditory Streams: Resetting by Changes in Location and Loudness. Perception & Psychophysics. 1998. 60. 1216–1227. 10.3758/bf03206171. free.