Time-stretching a sample involves changing its duration without altering its pitch, or vice versa. When you time-stretch a sample and then change its pitch, you introduce a variety of sonic implications, and these can be either detrimental or beneficial depending on how skillfully you manipulate the sample. The major issues that arise with time-stretching and pitch alterations are artifacts, and loss of perceived fidelity.
Implications of Time-Stretching and Pitch Shifting:
1. Artifacts: Time-stretching and pitch shifting algorithms often introduce artifacts, which can be unnatural sounds. These artifacts are created due to the complex processes of resampling and processing the audio signal. Depending on the method used, these artifacts can range from subtle phase issues, to noticeable glitching and ‘warbling’. Lower quality algorithms produce more artifacts, especially when extreme stretching and pitching are applied. The type of artifact created depends on the algorithm itself and the degree of manipulation. For example, a low-quality stretching algorithm that’s being pushed to extremes can cause a ‘smeared’ sound, or cause odd timbral changes, and even result in very noticeable pitch shifts and stutters that are not intentionally created by the producer. Another typical artifact is known as ‘granular’ artifacts where the audio sounds like a collection of small audio ‘grains’ because of the stretching algorithms attempting to reconstruct the sound based on small audio pieces.
2. Timbral Changes: Time-stretching can alter the timbre of a sample, particularly when done aggressively. A sample stretched too far may lose its original punch, warmth, or clarity. For instance, a drum hit that originally had a sharp transient could sound dull and flattened when stretched significantly. Pitch shifting can also alter timbre, as lower pitches may lose higher frequency content and higher pitches ma....
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