richardein wrote:Shooshie,
Yes, I'd verymuch like to read what you've written about the virtual pianos in general. I may know some of it, but I'm certain I'll learn quite a bit.
Ok... Here it is:
[
the unpublished sidebar to the Akoustik Piano Review.]
Background on VI Pianos
Virtual Piano. Not just any old sampler.
Just what is a "great" virtual piano? Thank you for asking, because I think the answer is critical for understanding the emerging piano shootout. Have you ever wondered why so many samplers and synths produce fantastic flutes, but pitiful pianos? Complexity is the issue. A flute is a whistle on a piece of pipe, and is thusly one of the simplest of pitched instruments. A piano is an 18th century Italian technological marvel, perfected largely by Steinway in the USA in the 19th century. It has about 230 strings zig-zagging through 88 notes, stretched to a tension of up to 35 tons of pressure on a steel frame, pressing on a wooden bridge over a wooden sounding board. Hundreds of patents by companies like Steinway (which is, contrary to popular belief, a proud American company with a branch in Germany) changed the instrument from a drawing-room delight to a singing powerhouse that could hold its own in the din of a 100 piece orchestra. There are over 9000 parts, half of them moving, in a concert grand, and the action is a mechanical marvel. Capturing the incredible sound of these beasts has been considered impossible for makers of synths and samplers. Few even try to get it exact. The answer for those who need an actual piano sound has always been... an actual piano. Until now.
Sampled instruments, whether in hardware rack units, keyboard units, or software Virtual Instruments, require an actual recording of about every 4th note in the chromatic scale, which is then transposed to produce the in-between pitches. The more recorded pitches, the less transposition is required, and there will be more unique sounds since more notes were sampled.
To Loop Or Not To Loop
There are two basic types of sample recordings: those which loop, and those which sustain until their sound completely decays. The latter are generally percussion instruments or plucked instruments. Any sound which must sustain indefinitely, such as a flute or horn holding a long note, must be looped. Those samples can often be exceedingly small, since the looped portion begins right after the attack, and need not be very long. Drums also can be very short, since they decay to silence quickly. But pianos are another matter. The longest tones on a piano are generally the lowest octaves, and those may sustain for over 30 seconds. That is a long recording to keep in RAM. No hardware-based piano sample I've ever heard actually sustains the entire note. Instead, it either loops after a certain point, or switches to a synth-hybrid that sustains until the key is released. This is why many virtual pianos sound pretty good initially, but quickly end up sounding like your kid's Casio. For ensemble work, that's often enough to do the job--just enough to fool the ear into believing there's a piano in the mix. For solo work, however, a good sample must endure for the entire fade of that string. That's the first order of complexity as regards a fine virtual piano.
Attack!
The second point of complexity is the levels of attack. Few instruments sound the same when played loud or softly. In fact, in most instruments, "loud" is not so much a measure of decibels as it is of harmonic richness. Soft tones are less complex. That is certainly true of pianos, for which a soft tone in the mid-high register approaches (but never reaches) flute-like simplicity. So, each pitch must be recorded at multiple volume/velocity levels to capture the harmonic content of that loudness. Some virtual pianos have maybe four sampled velocity levels, from which all the other velocities are extrapolated. Others have six. Ivory, released in 2004, had eight velocity levels, affording it a tremendous difference in realism. Native Instruments' Akoustik Piano has a whopping ten levels. Already we've been talking about 30 second recordings per pitch for lower octaves. Now we're multiplying that by 8 or 10! That requires a lot of memory! Old piano samples were considered complex at 30 megabytes. Now we're talking about samples that weigh in at 12 GB. No hardware sampler has that kind of RAM. In fact, few computers really have that kind of RAM, especially for a plugin.
Row, row, row your note, gently down the stream...
And that brings up the more-or-less recent breakthrough that has made complex virtual pianos possible: streaming sample technology. So what's the deal? The audio plays in real time, right off the hard drive. "What's new about that?", I hear you ask. "All recordings stream, don't they?" Yes. But we're talking about 88 channels of streaming audio in one piano, one of which must play the instant you hit any key. Most people do not play all 88 notes of a piano at once, so we can knock that down to, say, 25, 40, or 50 channels (voices, or polyphony, however you wish to call it), but that's still a massive amount of audio to stream. Nonetheless, digital audio workstations like Pro Tools or Digital Performer have been doing this for over a decade now, so the technology has been there. It's been a matter of harnessing it for virtual instruments.
A good segue...
To stream virtual instruments, a little of the sample is kept in RAM, because it cannot predict what note you're going to play, and that has to react instantly to your fingers on the keyboard. That gives your VI a few milliseconds to put your hard-drive in action, locate the appropriate sample, and load the rest of it. If done properly, it segues from the stored sample to the streamed sample without you ever knowing about it. As long as your computer and hard drive are up to speed, this is not a problem. Slower computers will just invite frustration. Good VI engines allow you to adjust several parameters so that you can compromise performance for quality. Thus, you can use a streaming VI on a slow computer if you don't mind waiting for a delay after each note. That makes live performance out of the question, but you may still get some functionality for playback of recorded tracks. Each computer setup will have its sweet-spot, the point where the compromise yields the greatest quality with the smallest delay. Adjusting the VI for that sweet-spot is critical if you want to avoid pops, clicks, and sometimes more severe side-effects. Fast computers rarely ever have problems. You can pretty much select all the high-performance options on a G5 dual 2.0 GHz PowerMac and never look back.
Pedaling right along...
So, we've talked about looping vs. self-contained samples, velocity levels, and streaming, but there's more. A good piano sample can't be complete until it simulates the effect of the pedals. Traditionally, the sustain pedal (controller 64) simply diverts the MIDI-off command until the pedal is released. That leaves the notes playing together, which is what happens on a piano, right? Wrong. On a real piano, the sustain pedal releases all the dampers on all the strings, and so the unplayed strings pick up sympathetic vibrations and begin producing their own sounds, which emphasize certain harmonics and create a dynamically rolling chorus effect. Until very recently, no piano sampler has even attempted this. Akoustik Piano not only does it, but does it well enough to convince all but the most sensitive of ears that the piano they are hearing has real vibrating strings. The introduction of a chorused effect with the application of CC#64 was a major step forward. But that's not all. There are two other pedals on a modern grand, and very few samplers have even acknowledged their existence. The una-corda pedal, or "soft pedal," on a modern grand shifts the entire keyboard over a little less than a centimeter, which causes the hammers physically to miss all but one string (una corda) apiece. This produces not only a softer sound, but a less complex timbre. Akoustik Piano responds to controller #67 with its own version of a una-corda sound. Finally, the last pedal, known to most people as "the middle pedal," but known to pianists as the "sostenuto pedal," has the function of sustaining only the keys that are depressed at the time it is applied. Other keys still play as if no pedal is applied. Akoustik Piano's manual claims that it responds to CC#67 as a Sostenuto pedal, but this is a misprint, since CC#67 is used for the una corda pedal. They intended CC#66, the correct controller for Sostenuto.
The difference is in the details...
Those are the piano basics for a great virtual piano. Other features are optional, including simulating the distance to the microphones, open or closed lid, room sounds (reverb and reflections), touch compensation (matching the playback velocity with your keyboard), listener perspective (audience or performer), stereo width, EQ, tunings, transposition, key noise, pedal noise, and panning. Akoustik Piano has specific controls for all these things, and even more, as is discussed in
the main body of the review.
Shooshie
(written in early November, 2005)
