Author: Tata Cheng

Another method to record in Pure Data is record through writesf~ object. To do so, it have to send three command into writes~ object, open(create) a wav file, start and stop recording. The problems is if I just use open_[filename], then I would overwrite the last recording. In order to record multiple tracks, I have to make a system that will change file name every time I press open. In order to use one bottom to record and stop (which is the toggle), I used number box and moses object to trigger the record system. When the toggle on, it would be one in number box, and that will trigger the bang in the right to create file and record; when it off, it will trigger the bang in the left and the bang will send signal into message stop. By using integer object to store and recall number and feed +1 object next to it, it will create a loop, and every have bang in, it will +1 to the number that store in integer object. Then the number go into a makefilename object. In the message section, use $ to indicate the various number. As a result, every time when press record, the file name will increase in one from zero. That overcome the overwrite file problem.

As my project is to do recording with Bela, I started to explorer how can record in Pure Data. One of the method is to use the array to capture sound wave. Using ads~ object to convert analog audio signal into digital then use *~ object to control the input signal. In here, I found that can use env~(an envelop follow) with vu meter to track the input signal. Then using tabwirte~ object to send and write data into a table. In order to record one second sound, I have to set the table size into 44100 which is same as the input sample rate (as sample rate in the sample past thought per second).

On the other side, it start with a toggle to run the metro which its speed is control by a Hsilder. Then it send in to a bang that would trigger tabwirte object instantly and send it into a delay object (which I found later that have to type in argument, the patch in above didn’t have delay effect at all) and it trigger the message, and it send 0 and the sample rate and time in to a vline~ object. And the line object send argument into tabread object to play the sound. When I was trying to play this patch with my computer microphone and speaker, it create a feedback loop which create an interesting sound. The speed of the metro affect the sound as it trigger both record and play sample which adding like a gate that chopping the feedback loop. It also create a short attack effect which almost like a kick drum sounds. It was fun, but I found that using this method are good for do short sampling, not suitable for field recording.

At first, when I thought to capture more information like temperature and humanity in the field, my first instinct is build a microphone by changing a mic capsule. Using a mic like objects to do field recording seems to be the straightforward way to do that as field recordist so used to pointing or setting up a mic/mics in the sound source or specific point. However, after I chat with Milo and Joanne, I found that it would be so difficult to make something like that. First of all, mic capsules work different form those sensor. Mic capsules transferring the vibration from the air to electric signal using the magnetic diaphragm, but the sensor is sending out electronic signal. Then I thought, is it possible to use the sensor electronic signal to modulate the audio input (a mic signal). It is possible to do that, but then need a lot of try and error, as Joanne suggested that I can not be done in just one or two months time. Both Milo and Joanne suggested me to use computer like Bela or Arduino. If I use computer, then I can map the sensor data into anything using coding. Working in the way is more accessible and have more control of the data from the sensor. To choose between Arduino and Bela, seems Bela is the better option. As I want those data of the sensor affect the audio in real time, Bela seems is a better choose for processing audio, plus Bela can run PureData which is the only programming language that I have more knowledge with.

To explore more in pure data, I follow the tutorial in archive.flossmanuals.net/pure-data/. In pure data, they only have two type of oscillator, osc~ object create sine wave and phasor~ object create sawtooth wave. Although with some mathematical equation, we can transform those wave into other type of waveform. I was trying to make triangle wave, but the math part really so difficult for me. When I was doing research on how to do that, I found there have another way to create different type of wave which is using array, a table in Pure Data. In the exercise in class, we used it as a wave from monitor to see what wave we have created. However, we can actually read the table and use it as a wavetable synth.

This time using Hslider to control the in put and convert it with mtof object to frequency. Then the function of the phasor~ object is sent out audio signal from 0 to 1 and multiply 2051 which is the length of the table. Then the most important part is tabread object, which can play the table as audio signal. Then I come cross with new box which call Message. Message box can send a number or a command into object box. In the tabread~ object, I send three different message called set waveform, then my pressing it, I can change the tabread object to read different table. The trick of using array is set a common in a message box: first type the table name, then can set it to sinesum with the length and the point. This message can create a desire graphic in the array and use the common normalise 1 to make sure the graph won’t clip and stay inside the table. Then finally sent the tabread signal into *~ 0.5 to low down the volume and sent it into dac~. In addition, I can also use the mouse to draw the graph (waveform array) to create interesting sound as well.

I made my first PD (Pure Data) patch. By doing this, I learned the basic of pure data. Firstly, object: The Rectangle boxes that can type in command and different command works differently. For example, osc~ is oscillator, mtof is midi converter, key is the signal receiver from the keyboard. Object with a ~ signal is the audio signal which have a thicker line with connect to and other object and the thin line is message or number. Object box can also can do math such as * for multiply and it can be use as VCA in pure data to amplify signal. Another type of box is number box. It can show the number of the inlet (signal in) or can change the number in play mode (command + E to toggle edit and play mode). Finally the most important object is the dac~ (digital to analog converter) which basically work as an output.

The patch I made is an additive synth. Firstly used the key object to control changes and used mtof object to convert signal. Then the main first oscillator set in 440 hz. The first number box sent number into four extra oscillator, and use * object to modify the number that can create a harmonic sequence. Then every sub oscillator have different volumes by using *~ object. All the signal go into a *~ 0.25 to limited the final output value to prevent clipping and send that into dac~.

Margaret Tait, a poet and filmmaker, who born in Scotland. At the age of 8, she was sent to Edinburgh to be educated. She studied medicine at Edinburgh University. Then she became a doctor at some point till she went to Rome to study filmmaking. Her scientific background shaped some of her art work, which doubts about reality and existence. It shows in some of her poems and films.

Litmus - Margaret Tait
I don’t know why is that acid turns blue litmus pink,
    And don’t tell me you know
    Because I’m sure you don’t
    – ‘Because it’s acid.’ –
    That’s no reason.
    Acid is pink.
    Nonsense.
    With other reagents the pink’s on the other side.
    Why pink?
    Why blue?
    Why change?

The short film Aerial combine different footages of rural city, nature, birds, the sky, rain drops, etc, alone with single piano sound and nature sounds. According to Tait, it ‘touches on elemental images. Air, water (and snow), earth, fire (and smoke), all come into it. For sound theres a drawn out musical sound, single piano notes and some neutral sounds.’ She stated that it is ‘just as a sort of song or even a kind of nursery rhyme‘. Four difference elements just intermingle and it didn’t have narrative and argument. It just shows the reality in a poetic way.

For me, I like use field recording as only material to compose and what is reality is the main argument in this field for long time. There is not reality in field recording as it transfers vibration into electronic and invert it back to vibration in the speaker later. In this process, it lost reality. The recording we listen it back is difference from what the recorder hear in the recording environment. The recorder can’t capture everything, thus it is the recorder chooses. People wouldn’t choose listen to the same things in the same environment. The other problem is other sensory. When we are, for example in the forest, sensation other than vision and hearing, for example temperature and humidity, would change our experience. Those sensory experience can also shape the way of listening.

Therefore, I am thinking is it possible to capture more elements while doing field recording, and by doing so, can field recoding practice can be more accurate and more close to the reality?