If mem­bers of the audi­ence packing 318 Curry Stu­dent Center yes­terday after­noon closed their eyes, they may have felt trans­ported to a New Orleans blues bar — cour­tesy of the piano stylings of Murray Gibson, dean of the Col­lege of Sci­ence.

But that “bluesy” sound the audi­ence heard does not arise nat­u­rally from a modern piano’s keys. It took cen­turies of lit­eral fine-​​tuning to create the broad musical palette that char­ac­ter­ized the playing of Jelly Roll Morton and rag­time legend Scott Joplin.

Sound,” explained Gibson as he launched into a lec­ture enti­tled “Physics of the Blues” high­lighting the origin of har­mony and scales in Western music, “is a pres­sure wave hit­ting your ear.”

Each note Gibson played issued a wave vibrating at a char­ac­ter­istic fre­quency, along with all of its “har­monic” waves, or those vibrating exactly two, three, four times as fast. As he put it, “When two notes are played at the same time, if they have over­lap­ping har­monics, they’ll sound con­so­nant to your ear.”

Nearly 3,000 years ago Pythagoras con­structed the first known scale from scratch, adding one note to the next whose wave fre­quen­cies had the ratio 3:2., known as a fifth. The resulting pen­ta­tonic scale con­sisted of the notes C, G, D, A and E, Gibson said. “In almost every civ­i­liza­tion, this scale has emerged,” he explained. “You can play these notes in any com­bi­na­tion and they will sound good together.”

Keep adding fifths, Gibson noted, and you get the classic dia­tonic scale we all remember from “The Sound of Music”  (do, re, mi, fa, sol, la, ti). The problem with this approach is that if you con­tinue to add per­fect fifths, you will never join Maria back at “do.”

After seven notes, you are within one per­cent of the orig­inal fre­quency. To get closer, Gibson said, you must add another 22 notes — far too unwieldy for the human musi­cian. So, we set­tled on a seven-​​note scale and that suf­ficed for a few millennia.

Then, 400 years ago, Bach was born. At the time, if pianos were tuned to the key of D, songs com­posed in the key of E sounded ter­rible. But Bach wanted more com­plexity in his com­po­si­tions and a broader palette with which to shift between keys inside a single fugue or can­tata. To over­come the need to re-​​tune his instru­ment mid-​​song, a new “well-​​tempered” scale emerged. Orig­i­nally per­ceived as “the Devil’s scale,” it required each key to be out of tune by the same small amount.

Together they sound okay, because they are all equally out of tune,” Gibson said.

But this tem­pering left out an impor­tant note — the blue note. Cen­turies after Bach, Morton and his con­tem­po­raries wanted to bring African sounds into Western music using the existing scale. In the key of C, the blue note resides some­where between E flat and E, where no piano key exists. To get there, the orig­inal blues pianists invented the tech­nique of “crushing” notes together — playing E flat and E simul­ta­ne­ously. Crushing was “an effort to get at a note that is missing from our sophis­ti­cated Western scale,” Gibson said.

It cre­ated in its own way, a very rich, com­plex, and inter­esting musical genre which is unique to this sit­u­a­tion,” he explained. “It wouldn’t be the same if the key­board were to have the right note.”

Gibson assured his audi­ence that he wasn’t trying to decon­struct music. Instead, he said, he wanted to empha­size the com­mon­al­i­ties “between the physics and math­e­matics that drive it and the cre­ation and inter­pre­ta­tion of music.”

The brain, he added, must be using some of this when we sit back and listen to the blues.