Tutorial 2: Creating Instruments using Master Tuning

In MetaSynth 2.5, presets in the Image Synth have an associated Fundamental or reference pitch. The reference pitch determines the pitch at which the pixels in a picture play back. In earlier versions of MetaSynth A2 (220.5 Hz.) was always the reference pitch. There are a number of uses of this powerful feature. In this tutorial, we use it to generate samples at different pitches from which we will then build a MetaSynth instrument.

Step 1. Computing the First Note

A) Select the preset
Bring the Image Synth window to the front and open the tutorial presets file.
Click on the Preset pop-up menu  and choose .

B) Set the fundamental (reference pitch)

Note this display in the upper-right hand corner of the Image Synth window.  The display indicates that A2 is the reference pitch associated with the picture. Clicking on the up or down indicator will move the fundamental up or down by an octave. To change the reference pitch's note, click on the Master Tuning icon .

Press the down icon to set the reference pitch to A1.

C) Compute and Save the sample
Press  to compute the sound. Save the sample to disk by choosing Save from the File menu. Type 'Tau A1' into the Save dialog box and save the sound. The 'A1' at the end of the sound's name is used by MetaSynth to automatically map the pitch of the sample when building an instrument. It is also a useful reminder of the sample's pitch.

Step 2. Creating the Rest of the Samples

A) Transpose to next octave
Press the up icon in the reference pitch display area . The refererence pitch will be set to A2.

B) Compute and Save the sample 
Press  to compute the sound. Note that the sound is pitched an octave higher than in the previous step. Choose Save from the File menu and type 'Tau A2' into the Save dialog box, and save the sound.

C) Repeat this process to create A2, A3 and A4, saving each sound with the appropriate suffix.

 

D) Choose another note

In order to reduce the amount of pitch-shifting in our instrument, we are going to create a second sample in each octave of our instrument. Click on the icon to display the Master Tuning dialog box

Choose D# from the notes popup menu (indicated by the triangle). Click on the octave number and type '1'. (If you prefer, you may drag the mouse over the indicator to change the value.)

NOTE: D# was chosen because it divides the octave evenly half.

E) Compute and Save the sample 
  Press  to compute the sound and save the sound with the appropriate name ('Tau D#1').

F) Follow steps A through C to create 'Tau D#1', 'Tau D#2', 'Tau D#3', 'Tau D#4', and 'Tau D#5'.


Step 3. Building the Instrument

As mentioned in the MetaSynth Reference Manual, MetaSynth can automatically build multi-sample instruments if the samples are named with their base pitch.

A) Choose Build Instrument... from the Instruments menu.

B) Choose any of the samples you saved in the previous two steps.

The Instruments dialog box will appear. Note that all the samples have been loaded into memory and automaticallly mapped to key ranges centered about their base pitch. Press   to save the layout on disk and name the instrument. Call it 'Tau Instrument'.

NOTE: MetaSynth automatically sets the base pitch of each sample and maps the ranges for the samples if the sample files names end with a pitch indicator (A0, A1, etc.)  When MetaSynth maps the key ranges it sets the max key parameter such that the base pitch will fall in the middle of the range assigned to that sample. This minimizes the pitch shifting that needs to be done to the instrument's samples.

Press  to dismiss the dialog and make the instrument available.


Step 4. Using the Instrument

A) Click on the Preset menu  and choose the second preset .

B) Set the sound source Click on the Sound Source icon and choose the new instrument . In MetaSynth 2.5, clicking on the Sound Source icon displays a pop-up menu of the sound sources available to play the picture, including instruments opened with the Open Instrument menu command.

C) Press the Preview or Compute icons ( or  ) to hear the sound.

CONCLUSION AND NOTES:
You have learned how to create an instrument "on the fly" using Metasynth synthesis.

Depending on the type of sounds you create,  you may want to use more (or fewer) samples per octave than in our example.
Usually having two or more notes per octave is sufficient for a high-quality instrument (Commercial sample libraries for samplers often space the samples by a fifth). For synthetic sounds where the harmonic content is not particularly dynamic, creating one sample per octave may be enough. Pitch shifting slows down or speeds up sample playback. In some cases, if the samples are harmonically dynamic or if it is important for the notes' harmonic envelopes to maintain the same rate, you should create more samples per octave to minimize the effects of pitch shifting.

 

IDEAS FOR FURTHER EXPLORATION:

In the example above, we used the same picture for all samples in our instrument. Interesting instruments can be made by mapping completely different sounds across different key ranges. For example you may want fewer harmonics for the high notes in a picture. To do this,  apply a low-pass filter between each pass.

It can be interesting to build instruments which are made up of a sine wave for part of their range and 'true' samples for other parts. This is an especially nice technique when you have a preset that uses sine wave synthesis to which you would like to add a simple drum or bass part.

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