This CD has featured a number of curiosities concerning speech, and also concerning music. Finally, we examine the mysterious no-man's-land between the two, and show how fragile the boundary between them can be. Composers throughout the ages - Monteverdi, Mussorgsky, Steve Reich, and Jean-Claude Risset to name a few - have played with relationships between speech and music, either by composing music that has some of the qualities of speech, or by embedding short segments of speech in musical contexts.

In particular, Mussorgsky has argued that music and speech are in essence so similar that with practice a composer could even reproduce a conversation in music. As he wrote in a letter to Rimsky-Korsakoff:  'whatever speech I hear, no matter who is speaking...my brain immediately sets to working out a musical exposition for this speech'.

In our final demonstration, speech is made to be heard as song, and this is achieved without transforming the sounds in any way, or by adding any musical context, but simply by repeating a phrase several times over. The demonstration is based on a sentence at the beginning of the CD Musical Illusions and Paradoxes. When you listen to this sentence in the usual way, it appears to be spoken normally  - as indeed it is. However, when you play the phrase that is embedded in it: 'sometimes behave so strangely' over and over again, a curious thing happens. At some point, instead of appearing to be spoken, the words appear to be sung, rather as in the figure below. 

Play Deutsch's 'Sometimes Behave So Strangely'

After listening to the repeated phrase, listen to the full sentence again. You might find that it begins by sounding like normal speech, just as before, but that when you come to the phrase that had earlier been repeated: 'sometimes behave so strangely', the words again appear to be sung.

So I leave you with a conundrum: Why should the simple repetition of a phrase, without any change at all, cause our perception to shift so dramatically from speech to song?

Listen to the WNYC Radio Lab interview with Jad Abumrad and Robert Krulwich about "Sometimes Behave So Strangely" and perfect pitch.

The illusion "Sometimes Behave So Strangely" experienced by the fifth graders of Atwater School, Shorewood, Wisconsin. Video created by their music teacher Walt Boyer, posted with permission.