Metropolis is a Fritz Lang 1927 science-fiction movie. It is a silent film and the score was composed for a large orchestra by Gottfried Huppertz: he tried to mix the classical world with some more modern sounds to emphasise its industrial and apocalyptic environment. This movie is considered to be the pioneer of the science-fiction genre and has inspired a lot of contemporary production styles.
The target of this project was to create both non-diagetic and diagetic sounds on a selected extract from this movie, using only modulation synthesis and trying to reinterpret only the frames, without being influenced by the original sounds.
The non-diagetic sounds are everything whose source is not visible and is not intrinsic to the action. Some examples within this category could be: the soundtrack (mood music/score) or the sound effects which add to the drama.
Four instruments were created thanks to modulation synthesis and all of them were created by the Operator (digital synthesizer) in Ableton.
The first one is a high-pitched sine wave with an LFO constantly modulating both its filter and its amplitude. When the amplitude of a waveform is modulated, this synthesis is called AM synthesis (Amplitude Modulation Synthesis). If the modulating wave rate is below 20 Hz, the tremolo effect is audible on the original wave form but, if it approaches the audible range, it is more difficult for the human ear to detect each individual amplitude fluctuation in the carrier and “sidebands” are produced. The frequency of these sidebands (which are usually inharmonic overtones) is the sum and the difference between the carrier and the modulator. If we are modulating a complex tone made up of more than just one frequency, two sidebands are produced for each. A good reference for this kind of synthesis is to be found in some of the Karlheinz Stockhausen works. Anyway, the idea of this non-diagetic sound was to create a constant harmonising looped high pitched drone to go with the whole frame for a sense of tension. The bass takes on a similar role and, with his fast arpeggio and boomy sound, it aims to keep the viewer’s attention. In order to further enhance this, and to raise the tension level, some automation on the bpm of the entire track was added to speed up the whole soundtrack right through to the end. This was to typical of the famous Jaws 1975 movie theme in which the shark is never seen but when the particular sound is heard, everybody is aware of its presence and, when the animal gets closer, the interval is ever shorter.
In the middle range two other instruments with the same modulation were created and then everything was panned and mixed to fill out the space properly. Thence, some volume and filtering automation were set up too, to facilitate arranging.
All the sounds whose source is visible on the screen or whose source is implicated to be present by reason of action are called diagetic. This reference-category can be found in Forbidden Planets (1956): this was one of the first movies in which synthesis was used.
Numerous samples of diagetic sources appear in this piece of audio so it was really hard to distinguish between them, create, synchronise and mix them. The working process was based on creating one sound at a time, repeating it whenever necessary (with proper editing when needed) and mixing it with what had already been created. Some of these sounds were created by using AM synthesis like the sound of the lighting cylinder at the very beginning: here the amplitude of the triangular waveform (in digital VCO A) is modulated by the Operator LFO with a high rate but a low amount. The sound of the switch, as all the others in the project, is created in another track by an envelope with a short attack and fast decay linked to the noise.
The rest of the sounds are mostly made most by FM synthesis (Frequency Modulation synthesis). This technique was developed by John Chowning in the 60’s and is based on modulating the frequency of one oscillator with another one. When you put two oscillators (or more) in series, the pitch of the first one is modulated by the next. If the rate is below 20 Hz a vibrato-effect is reached but if you feed it at a faster rate, then sidebands are created. It is similar to AM but, in this case, more than two sidebands are created relating to the feeding oscillator amplitude. Most FM result in a very clangorous and a-tonal sound. The way to make it sound harmonic is to use harmonic ratios between carrier and modulator frequency. An example of FM synthesis in this project may be found with the energy rings sound (fluctuating around the robot). Here four oscillators in series were employed and they were automated so that they are turned on one after the other depending on the number of rings we see on the screen. All the waves are sine waves, to get a rounded effect and the automation is carried out while the scene is changing to make it un-noticeable.
Some other sounds were created using both AM and FM synthesis. An example of this is electric noise: a sine wave is feeding a squared wave and the LFO is modulating both the filter and the amplitude of the sine.
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