3. PEDAL IN LISZT’S PIANO MUSIC
4.4 The envelope and spectrum of piano tones
It is possible when the pianist plays on one instrument that the audience can perceive the same tone with a different timbre. In that case the pianist has probably played this tone with a different dynamic. The degree of loudness can somehow influence timbre by favouring higher overtones. Playing the same tone with different volume levels also changes the shape of envelope.
Thus, the volume of the sound is in close relation to both determining components of timbre, spectra and envelope, and in practice it is very difficult to distinguish between the exact volume and timbre of the piano’s tone. !
!
As mentioned above, the pianist cannot practically influence the timbre of a single tone. The situation changes when more than one note is played. In a chord, a pianist can influence the loudness of each voice. When the volume of a tone in the chord changes, the complex vibration then has a new overtone constellation, hence the sound quality of the chord is also changed. !
!
The timbre can also be influenced by the manner in which two or more tones, following each other, are bound. In legato playing, the first key is not to be released until the next key is pressed down. If the first tone is held over the beginning of the next one, the smooth change of timbre in the manner in which the dampers fall onto the strings can help to achieve better legato.
Legato is therefore not only a result of the duration of the tones, but is also enhanced by factors of timbre.!
! !
!
4.4 THE ENVELOPE AND SPECTRUM OF PIANO TONES!!
As has previously been reported, the spectrum and the envelope are two factors that determine the timbre of the piano. Figure 4.1 shows the envelope of a piano tone. As we can detect from the figure, the most considerable event in the piano’s tone occurs at the beginning of the envelope. With the
attack transient , the hammer gives the impulse to the string(s), after which 5 the loudness decreases step by step. Thus, it is the initial interval (of the 6 envelope) that primarily determines the piano’s sound. The piano’s sound on the tape will not be recognizable when this initial interval (attack transient) is eliminated, or in the case that its location is not at the beginning of the sound.7!
!
Figure 4.1 Envelope of the tone c1 (262 Hz) during 1.000 ms (1 second) played on a modern Steinway.!
!
Attack transients consist of changes occurring before the sound reaches its steady-state
5
intensity.
To be precise, the loudness decays in two phases. During the first phase the amplitude’s
6
level decays, after a loud initial impulse, rather quickly to a certain level. In the second phase, the amplitude’s decay will continue, but much more slowly. These two phases are easier to observe when higher frequencies are in question, as in Figure 5.4, for instance.
In this case the first phase changed into the second one between 200 and 250 milliseconds after the attack transient, depending on the piano used.
In 1987, A. J. M. Houtsma, T. D. Rossing and W. M. Wagenaars demonstrated an
7
experiment. They played a tape recording of a piano backwards so that the attack transient occurs at the end. The sound is more suggestive of a reed organ than a piano.
(Rossing 1989: 294) For a second experiment they recorded the sound of different musical instruments, then cut and spliced the tape so that the attack transient was removed. Without the attack transient, it is much more difficult to recognize the instruments on which the sounds are recorded. Some pairs of instruments, like trumpet and oboe, or French horn and saxophone, sound remarkably similar. (Rossing 1989: 130) I made an almost similar experiment with three recorded tones on a modern Steinway: C2 (65Hz), c1 (262 Hz) and c3 (1047 Hz). In the case of each sound signal I removed the attack transient. The edited bass tone (C2) did not remind me of any classical music instrument. The most similar timbre might resemble a (toy) wind instrument. The middle register (c1) of piano without the attack transient sounds like a saxophone, and the treble (c3) one like a dulcimer (cimbalom). !
The spectrum changes over the wide range of the piano. In the lower register there are naturally more partials in our hearing range than in the higher register. In the case of C2 (65 Hz), for instance, as many as 30 partials can be detected; at c3 (1047 Hz), less than 10 partials can be detected. (Rossing 1989: 294) In Section 4.1 (Example 4.2, Diagram 4.1) we have discussed that the level of the 1st overtone (fundamental tone) is not necessarily the strongest. We can also find this phenomenon in cases of piano tones in a low register (Diagram 4.3). In the case of a high register, in contrast, every next overtone is weaker than its predecessor.!
! !
!
!
Diagram 4.3 !a) Spectral diagram of ! ! ! b) Spectral diagram of!! ! C2 (65 Hz) by 250 ms ! ! ! c3 (1047 Hz) by 250 ms!
after attack transient. !! ! ! after attack transient.!
! !
!
As we have seen in Figure 4.1, the amplitude of the vibration reaches the maximum level quite rapidly, in approximately ten milliseconds. Afterwards 8 the amplitude decreases. The higher and lower partials decay at different speeds, so the spectrum may change. Nevertheless, changes are quite accidental. In Diagram 4.4 the change in the spectral constellation of the piano over a short period of time is shown. (The spectra of a single tone played on the piano will be treated more exactly in Chapter 5.4.)!
! !
This data is gauged by Steinway. The duration of the transient attack can be different
8
with different piano makers. On a Chickering (1867), for instance, the maximum level of the amplitude builds up in 10–16 milliseconds!
(-db) 0
30
60
1 5 10 (partials)
(-db) 0
30
60
1 5 10 (partials)
!
!
Diagram 4.4 !a) The spectrum of the ! ! ! b) The spectrum after 500 ! maximum level C2! ! ! ! milliseconds from the!
! ! (65 Hz);! ! ! ! ! maximum point of the!
! ! ! ! ! ! ! ! tone C2 (65 Hz).!