Hi,
I have not a very clear view on the legato vs portamento stuff,
thus I'd like to discuss this with you:
I found these definitions on the net:
---
Legato Pedal:
When on, this causes a legato effect between notes, which is usually achieved by
skipping the attack
portion of the VCA's envelope. Use of this controller allows a keyboard
player to better simulate the phrasing of wind and brass players, who often
play several notes with a single tonguing, or simulate guitar pull-offs and
hammer-ons (ie, where secondary notes are not picked). If a MultiTimbral
device, then each Part usually has its own Legato Pedal setting.
----
What does this mean in terms of sample playback engine ?
(we are dealing with samples of real instruments, not with elementary waves
like in synths)
first, it seems to me that this only makes sense in monophonic
instruments (correct me if I'm wrong).
Does "skipping the attack portion of the VCA's envelope" in the case of a
sampler mean that we shoud skip the attack volume envelope, and play the raw
sample from the beginning, or skip the attack part of the sample too ?
(eg jumping directly to the sustain section, but this may not be possible
without clicks (a fast fadein might solve this problem, but I'm not sure if I'm
thinking in the wrong direction here)
--
Portamento:
Portamento is the effect produced when one note is carried smoothly on to the next
with no gap.
The pitches in between printed notes are briefly sounded. Stringed instruments
and the trombone often use this very legato effect. Portamento might occur on
all the played notes or it might only occur if the previously played note is
held down while the next one is played. The portamento time is the time taken
for the pitch to completely change from one note to the next.
------
this too seems to make sense in mono mode only, but again,
in the case of multisampled instruments there are some problems
even on RAM samplers:
BTW how does regular samplers behave in that case ? (multisampled instruments)
Assume we have a piano instrument and then play C1, and now we press the
C4 key: that means a difference of 36 semitones.
You can immagine that if we simply slide the C1 sample up 36 semitones, the
end result will sound quite crappy and hardly sound like a piano anymore.
Perhaps it would be useful to do some crossfading between the two notes:
first you hear only the C1 note, then you press C4 and the C1 sample
begins to slide up (with decreasing volume), while a C4 sample with a -36
semitones pitch begins to slide up with increasing volume.
At the end of the sliding phase, you will only hear the C4 sample.
Alternatively to avoid more artifacts, we could limit the cross fade range
within the +-N semitones around the middle point.
So that let's say from 0 to 13 semitones sample 1 is used, then between
14 and 22 ( 18 +- 4) , the samples are crossfaded, while from 23 to 36
sample2 is used.
comments ?
Basically I see no problems in implementing legato (without sliding),
if it's only about skipping some initial envelope/samples, but for
portamento, it is not a trivial task to do.
Benno.
On Thu, 21 Sep 2000, Ruben van Royen wrote:
> > >one more issue: portamento. (Mono&Legato playing causes sliding of the tone
> > >to the new pitch). Are we going to forbid this? A fast portamento can shift
> > >the pitch quite fast a few octaves up, for example.
> >
> > its no different than playing the entire range by hand, just very
> > quickly. as long as the sound associated with each note number is
> > already cached, no problems.
> >
>
> No. It is more like a very long pitchbend. The tone slides to the new pitch.
> Its use is a bit different than pitchbend, for example to imitate a sliding
> bass. My point was that it has the same effect on the engine, but is different
> for the musician. And it is less ordinairy to limit the portamento range than
> it is to limit the pitchbend range.
>
> Playing legato is a bit similar. Now the effect is that the attack is not
> retriggerd when you play a new key.
>
> Ruben
