Sound sampler [sic]



Sound Master, for the 48K ZX Spectrum, allows you to store

sound or speech into the computer's memory and replay it

afterwards. But it also allows you to reverse the sound,

replay it at eight different speeds, and with varying

echoes.

  The program itself is not very large, about 4K of Basic

and 2.5K of machine code, but the enormous chunk of memory

used to store the speech - almost 32K for four seconds -

caters for 48K users only.

  The first thing you see when the program has loaded is

the blue menu screen. You're presented with ten options,

numbered 0-9. They are:



  1. Record sound

This option allows you to enter sound via a tape recorder

or microphone which is attached to the Ear socket of the

Spectrum. After about four seconds, an OK message should

appear on your screen and the program then returns to the

menu. However, if this does not happen then you have

entered a wrong hex code between addresses 65025-65052.

  What this routine does is scan the Ear socket at a rate

of 64,512 Hertz, or 64,512 times per second, for a noise.

If it receives a noise, a click, it stores a 1 in its

memory. If it doesn't, it stores a 0. These 1s and 0s are

stored in memory in groups of eight, known as bytes. The

analogue sound is digitised.



  2. Replay sound

This option replays the sound you stored in the computer.

It is, in fact, the reverse of option 1. It converts the

1s and 0s from memory to clicks and no-clicks.

  This reproduces a sound which is quite recognisable. But

because of the low speed at which actions take place, and

the Spectrum's limited speaker, some ambiguity is unavoid-

able. Fantastic, clear sound is produced at a 17 mHertz

rate, while ours is produced at 64 kHertz. This is due to

the speed of the Z-80 microprocessor found in the Spectrum.

It is, in fact, quite a fast eight-bit processor, but for

out purposes not fast enough to produce a sound that is

free from disturbing noise. Using a Dolby cassette deck

would help in filtering out these noises, though.

  If we wanted a clear, solid sound for four seconds, then

we would need a computer with 256 times more memory than

the Spectrum, and which runs at least 256 times faster!

Perhaps a Cray-1 will do. If you have any problems here,

check your bytes between 65053 and 65085.



  3. Change speed

The program allows you to replay the sound at eight diffe-

rent speeds. Speed 1 is superfast - you'll need mega-ears

to understand any of it - and speed eight is the slowest.

Speed 7 is the one at which sound is always recorded.



  4. Disappearing echo

It is impossible to do any magic with the Spectrum's sound

speaker's volume under software control, so I present you

with a disappearing echo instead of a fading one. Echo-

steps may be controlled by the user. Echoing is done at the

current speed, set at option 3. This is initially 7.



  5. Appearing echo

Which is, of course, the opposite of option 4.



  6. Fastening echo

This produces an echo which starts at the current speed and

repeats, faster and faster, until it reaches speed 1. If,

for example, the current speed is 5, then the speeds at

which the program echoes are 5, 4, 3, 2, 1. If the current

speed is 8, the speeds are 8, 7, 6, etc. This option has no

effect whatsoever on the current speed at which sound is

replayed in option 2.



  7. Slowing echo

The echo starts at the current speed and slows down until

it reaches speed 8. Again, this command has no effect on

the current sound speed.



  8. Load file

Use to load a file previously saved using this program.

You'll be asked for a filename, but if you can't remember

the name of the file you want to load just press ENTER.

This command will only accept Sound Master files.



  9. Save file

When you have successfully sampled sound you may wish to

save it to tape. Enter the filename, start the tape recor-

ding and then press any key. Remember that 32,258 bytes

have to be saved, so saving might take as long as 2.5

minutes.



 10. Reverse sound

This handy routine reverses the sound stored in the micro.

This means, effectively, that if you had a recording in

your memory of you saying "computer" then the reversed

version would say "retupmoc". Intonation is also reversed.

This produces smashing effects.

  Note that this option does not produce any sound, yet

swops bits and bytes around in the computer's memory. This

means that every other option, except 1, now operates on

reversed sound.

  If you now save your file and load it back later, you

will notice that the sound is still in its reversed form.

To restore it to normal, just use option 0 again. Any

troubles in reversing your sound? Check your bytes 65108-

65150.