Music Synthesiser (Your Computer)Applications Creation Musical
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R. Mitchell synthesises a synthesiser.

I WANTED A PROGRAM that would enable me to alter the Env and Ent variables easily and quickly and then be able to hear them. I also wanted to see what the envelopes looked like, without having to resort to Pen and Paper to draw it each time.

The program I ended up with is just over 14K long. You can even use the keys like a music keyboard and once the sounds have been defined you will have a music synthesiser.

I've used plenty of Rem statements throughout the program, so I won't go into detail and describe what each part does. It is possible to move quite freely about within it when running.

After typing in the program, Run it and you will be in screen 1. This is the title page and there are five pre-defined sound on it. You can define up to nine sounds, the first five are not permanent, so these can be altered quite easily but for now type in 1 and enter it.

When you press the Y key will first get a prompt to enter your title. After you enter this title you will be asked if you want Noise, Play or both enter one of these by pressing the N,P or B key. The next prompt is for repeat on the tone, enter Y or N. These prompts and title are purely for your own reference and in no way effect the program.

You should still be at the point in the program where the computer is waiting for you to answer it. Do you want to add a new title? Press N for no. You will now sec a plotted graph — in white — of the volume envelope — screen 2. In the bottom left hand corner is the scale and the finished step. The scale can be altered by pressing Dor M. The D will divide the scale by 2 and the M will multiply it by 2.

When you start working on your own volume or tone envelope and the plotted shape goes outside the graphic window then by pressing the D key you will see the graph re-plotted at half the original scale. The same applies when the plotted graph is too small by pressing the M it will be re-plotted at twice the original scale.

The finished step tells you where you are in relation to the 0 volume level. On the bottom right hand side is the tone and volume time. This tells you how long the note you are designing will last and how much of it will be affected by the tone.

If you typed in 1 earlier you should have displayed on the screen what I think a Piano waveform will look like. There are two horizontal lines, the bottom one — green — is the 0 volume level and the top one — red — is the 15 volume level — maximum. If you go above the top line you will get some unusual effects, also the section step total at the top of the screen will change from red to green.

At the top of the screen are the step count, step size and pause time, with a green arrow pointing to the first one. As you enter new values for this the arrow will move to the next one. The program will check to see if the values arc correct each time you enter one, the arrow is controlled by using the cursor keys.

Press T and you will go to the tone envelope, this has one horizontal line and you can plot above or below it. Again in the bottom left hand corner is the finished step which tell you where you are in relation to the original frequency. Above this line increases the frequencies and below will decrease it. If you pressed 1 earlier then you will see a tone envelope for the Piano. Press E again and you will go back to the volume envelope.

If you Press C then all the values for the step count, step size and pause time will be reset to 0. This only applies to whichever envelope is being displayed, so if you have the Piano waveform displayed on the volume envelope screen — screen 2 — and press C then this is the only one to be affected, it will not reset the tone envelope unless you are displaying it.

Commands for screen 2.
C — To clear the variables.
T — to display the tone envelope shape and input new values.
E — to display the volume envelope and input new values.
M — to multiply the plotted graph by two.

D — to divide the plotted graph by two.
R — to return to the title page — screen 1.

cursor keys to move the input arrow.

P — to play the note or noise — screen 3.

You are now ready to play a note so press the P key. This will take you to screen 3. This is the last screen and you will have displayed in front of you the instructions for playing a note or noise. But I will run through them briefly:

O — this tells the computer that you wish to use the noise and note the period.

P — this plays a sound using the period part of the sound command.
E — return to the volume envelope graph and input mode — screen 2.
T — return to then tone envelope and graph input mode — screen 2.

R — return to the title page — screen 1.

cursor keys up and down, to increase or decrease the octave or noise level.

+ — this will put the tone on repeat.

- — this will remove the repeat from

the tone.

Q — this will automatically repeat the last note or noise played and keep on repeating it.

the left and right cursor keys will increase or decrease the speed at which the repeat occurs at.

W — this will cancel out the auto-repeat.

1 to 9 — By pressing these keys you are able to play another sound envelope, press 4 and you will get the Phaser envelopes to play, press 1 and you will get the Piano envelopes.

All the input commands are in the lower case, so don't use the Caps Lock or Shift keys.

On the left hand side just below the instruction on screen 3 you will see all the relevant information about the note or noise just played. Frequency, Period, Octave, Noise, Noise Range, Note Length — time, tone — vibrato — and name, as defined in the title page of the instrument or sound effect. So once you find the correct period or frequency of the note or sound effect that you are after, you only have to write it down. For example, Noise 6, and then press the T or E and write down the values you use in these two, step count, step size and pause time for each section and then you are ready to put them into your own program.

It is possible to use the keyboard to play a note across nine octaves, one octave at a time and you can play up to three notes at one time but only one noise. All the times that are displayed are in seconds.

I've used integer variables as much as possible to increase the speed and save some memory. If you want to make the tone envelope repeat in your own program don't forget to use a negative number when you define it e.g.:

ENT -2 or ENT -1 etc.

To alter the colours of the display: COL% PAPER, COL2% PEN 1, COL3% PEN 2, COL4% PEN 3
If for any reason you break out of the program then type in Goto 520 and you won't lose any of the variables that you have already entered.

Finally, Enter the following values into the tone envelope for the Piano.

Step count15
Step size10-2
Pause time201

Use octave 2, 3 or 4. All I'll say is it comes from India. Put a Rem on line 90 On Error Goto until the program is free from typing errors. Delete line 150 when everything is O.K. If you press the small Enter key, it will reset the colours and key speed.


★ YEAR: 1984
★ AUTHOR: R.Mitchell


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L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent  du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko.