Thursday, June 6, 2013

Pop song melody as a hierarchical sequence

Consider a piece of pop song melody. You may say it is a sequence of pitches. But if I simply randomly put all those pitches into a MIDI sequence and playbacked by machine, it may probably become a dead sequence. Namely, it does not convey any logically meaning.

So the melody does not contain only pitches. Pitches are the most direct phenomenon we got, but it's more than pitches. To simply extend below, pitches are modulated by the rhythms. Even considering a simple 4/4 time bar with 6 notes inside, there are infinite possibilities of rhythms. Each of them express a different musical feeling. So we take also the rhythm into our previous MIDI sequence, it sounds more logical, meaningful,but somehow still feels dead.

Something is still missing. When a singer sings, she not only sings out pitches according to the rhythms, but also expresses her highs and lows at the same time. These emotional highs and lows can be related to the pitches' highs and lows, but not exactly the same. The emotional feelings adds another layer above the pitches, which is called "dynamics". Dynamics can be simply understood as the loudness or velocity of a note. As you know, we can still do an experiment of dynamics within our MIDI sequence, but, as you may guess, it's still not perfect.

Now we have pitch, rhythm and dynamics, and what else?

Most of the time a singer sings each pitch at a time, but sometimes she drags a pitch here and there. And still some other times, she put an unnoticeable slightly lower or higher pitch slightly before the pitch she's going to sing. By such, the singer creates a smooth flow of sound. This is called articulation. Can we do articulation in MIDI sequence? Yes, but not as easy as the previous three. Simply because there is no simple way to encode articulation. Our effort to emulate a beautiful melody using MIDI sequence can safely stop here. But anyway, we discover the 4th layer of a pop song melody.

So pop song melody as a hierarchical sequence, from bottom to top, as I see, is: 1. Rhythm; 2. Pitch; 3. articulation; 4. Dynamics.


Google Translate:






所以流行歌曲的旋律,从底部到顶部,我看到的,作为一个层次序列是:1。节奏2。间距; 3。衔接; 4。动力学分析。


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