Experiments: slur vs. cross-fade

There are several ways of moving smoothly from one tone to the other. Today we are going to compare the two most common: slurring and cross-fading.


Gliding over the notes smoothly (sliding the tone).

Guitar slide

Guitar slide

The harmonics smoothly move to higher pitch, but remain parallel and in similar strength proportions during play time.


Gradually silencing one tone and increasing the volume of the other.

Harmonica crossfade

Harmonica crossfade

Each harmonic remains in the same pitch. The main subject of changes is the strength of harmonics.

Both effects isolated on a simple sine waves



Example A – one octave interval: 440Hz -> 880Hz
Falasol timbre file slur-octave.timbre crossfade-octave.timbre
Falasol spectrum graph falasol slur octave falasol crossfade octave
Listen slur-octave.wav crossfade-octave.wav
Spectrogram slur-octave crossfade-octave
Example B – small interval: 440Hz -> 453Hz
Falasol timbre file slur-small-interval.timbre crossfade-small-interval.timbre
Falasol spectrum graph falasol slur small interval falasol crossfade small intervalThe yellow glow indicates possible wave interference
Listen slur-small-interval.wav crossfade-small-interval.wav
(zoomed on x axis)
slur-small-interval crossfade-small-interval

On general cross-fade produces more rough sound texture. On small pitch intervals you can also observe the wave interference which results with tremolo effect – volume modulation (you can also see it on the real sample spectrogram).

Let’s see what is the impact of pitch interval on the cross-fade tremolo effect. Here is a sample consisting of 4 harmonics which pitch-up by ratio of 1.04:

falasol crossfade small rich

Falasol graph of 4 harmonics cross-fade up by x1.04

crossfade small rich

Spectrogram of 4 harmonics cross-fade up by x1.04

Tremolo speed is proportional to harmonics pitch and their interval, the tremolo strength is inversely proportional.

So far we have compared two tone transition techniques: slurring and cross-fading. However the real fun starts when they both are combined together. A remarkable example is the Shepard tone:

shepard-c falasol

Falasol graph of Shepard tone rising

SPectrogram of Shepard tone rising

Spectrogram of Shepard tone rising

The tone creates an auditory illusion of constantly ascending pitch. Please don’t listen to this sample when drunk or under influence of drugs.

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