Sound synthesis and signal continuity

Hi,

I am doing some experiments on sound synthesis. I've made a simple plucked
string sound synthesizer (with MIDI input), but I'm experiencing some
problems with the end of notes. When I hit and then release a key on my
MIDI keyboard, I can hear an annoying little sound because of the signal
going suddently to zero when I stop the note synthesis.

I tried to figure out how software like a basic MP3 player behave when the
user hits for example the 'Pause' button but I didn't manage to find
anything.

Do you have any insights on how to achieve a fast return to zero from an
oscillating signal?

Thanks in advance,

>Hi,
>
>I am doing some experiments on sound synthesis. I've made a simple
plucked
>string sound synthesizer (with MIDI input), but I'm experiencing some
>problems with the end of notes. When I hit and then release a key on my
>MIDI keyboard, I can hear an annoying little sound because of the signal
>going suddently to zero when I stop the note synthesis.
>
>I tried to figure out how software like a basic MP3 player behave when
the
>user hits for example the 'Pause' button but I didn't manage to find
>anything.
>
>Do you have any insights on how to achieve a fast return to zero from an
>oscillating signal?
>
>Thanks in advance,
>
>
>

If I understood you correctly, your notes stops when the note's signal is
not equal to zero yet. As you said the note has to sound after you release
a key, but volume of note has to tend to zero. In many cases it's enough to
multiply every sample by a coefficient that tends to zero.

randirandi wrote:
> Hi,
> 
> I am doing some experiments on sound synthesis. I've made a simple plucked
> string sound synthesizer (with MIDI input), but I'm experiencing some
> problems with the end of notes. When I hit and then release a key on my
> MIDI keyboard, I can hear an annoying little sound because of the signal
> going suddently to zero when I stop the note synthesis.
> 
> I tried to figure out how software like a basic MP3 player behave when the
> user hits for example the 'Pause' button but I didn't manage to find
> anything.
> 
> Do you have any insights on how to achieve a fast return to zero from an
> oscillating signal?

The simplest solution is the linear decay with the duration of ~50msec. 
The better solution is S-shaped transition of the volume to zero for the 
same duration. Both make for the soft muting/unmuting without the 
annoying artifacts.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com