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In this part we will have a look at the code and what you can do with it.
AMS files are plain text documents with the .ams extension instead of the .txt extension.
Each line of code is a command for the decoder inside Ableton Live that translates these text documents into samples. Some commands are better left unchanged, other commands are used to transmit values of specific parameters.
The Code
A AMS file generally looks like this:
AMS 1
Generate MultiCycleFM
BaseNote 69
RootKey 69
SampleRate 44100
Channels 1
BitsPerSample 32
Volume Auto
Sine 1 1000.000
Sine 2 794.328
Sine 5 562.341
Sine 6 446.684
Sine 7 0.355
Sine 8 0.355
Sine 9 354.813
Sine 10 281.838
Sine 11 0.355
Sine 12 0.355
Sine 13 223.872
Sine 14 177.828
......
......
Lets dissect the example I posted above.
AMS 1
Generate MultiCycleFM
The first line tells Live which format and format version the current file is.
The second line tells Live what to do with the data that follows.
To my knowledge, "MultiCycleFM" is currently the only generation mode available.
These lines are better left unchanged, changing them to a random command might render the AMS file unusable.
BaseNote 69
With this line you can set the base frequency of a note.
There are 2 different methods to input the base frequency:
MIDI Note Numbers: This can be a value between 0 and 127, but it is not restricted to the MIDI protocol. This means that you are able to create a AMS file with a decimal value like 36.50. When you play that AMS file in Live, it will sound like C1 + 50 cents. This opens up the possibility to create microtonal waveforms. More on that later.
BaseFreq: Instead of inputting "BaseNote 69", you could use the command "BaseFreq 440.0". Playing with this can only result into more microtonal goodness.
RootKey 69
RootKey is a command specifically for Sampler. It tells Sampler in which key zone the AMS file should be placed. This means you never have to map any keys to a AMS file, it is already done for you. These values are restricted to the MIDI protocol, so you can only use integer values from 0 to 127.
SampleRate 44100
The sample rate is the number of samples pers second, e.g. 44100 Hz,
and it can have any value up to 192000 Hz.
Channels 1
This parameter allows you to set the AMS file to be decoded as a mono or stereo file. 1 channel for mono, 2 channels for stereo.
BitsPerSample 32
Only 16, 24 and 32 bits per sample ("bit depth") are supported.
Volume Auto
This sets the volume of the AMS file. You can use values such as 0.5, 1, 2 or use the command "Auto".
When the volume is set to "Auto", then the volume of the AMS file will be normalized during decoding.
Sine 1 1000.000
Sine 2 794.328
Sine 5 562.341
Sine 6 446.684
Sine 7 0.355
Sine 8 0.355
Sine 9 354.813
......
......
......
This is the tricky bit. These values are used to generate the shape of your waveform.
Each line represents an oscillator that plays a sine wave. Every "oscillator" is pitched to a different harmonic.
By combining different harmonics, you can create a variety of waveforms.
The line is made out of 3 parts.
The first part "Sine", can also be a "Cosine". Just name it "Cosine".
The second part is the number of the harmonic. The AMS specification can take up to 96 Sines + 96 Cosines.
The third part is the volume level of the individual harmonic. This can be a value from -1000.000 to 1000.000. When you use negative values, you are basically reversing the phase of the waveform.
Here are a few examples of how the waveforms look like:
By combining Sine and Cosine waves into a different waveform, you are able to create basic shapes such as a square, saw or triangle. But you are also able to create waveforms with a more unique and complex shape.
This is how the harmonics of a square look like:
Sine 1 127.324
Sine 3 42.440
Sine 5 25.463
Sine 7 18.186
Sine 9 14.144
Sine 11 11.571
Sine 13 9.789
Sine 15 8.482
Cosine 1 0.391
Cosine 3 0.391
Cosine 5 0.391
Cosine 7 0.391
Cosine 9 0.391
Cosine 11 0.391
Cosine 13 0.391
Cosine 15 0.391
Microtonal AMS files
As I mentioned in the previous part of this piece on AMS files, I spent a bit of time to experiment with microtonal scales.
I made the easiest set of files, a set with 24 notes in an octave. Each consecutive file is pitched 50 cents higher then the one before.
I started at C1, so the BaseNote and Rootkey are both 36.
But on RootKey 37 (where C#1 should be), the BaseNote is 36.50. Which is equal to C1 + 50 cents.
You can download the files in a little project that I prepared for you. It contains a Sampler preset with the AMS files preloaded.
- Click here to download The Covert Operators: MicroTonal Square Project
Thats all I can say about microtonal AMS files at the moment. We still haven't covered all the great things you can do with the files that are actually in tune.
In the next part of this piece on AMS files, we will have a look and a listen at how these files sound like and what sort of sounds you can create with them.
I hope you enjoyed this and I will see you next time for a deeper look at this great format.
Take care!
- The Covert Operators
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