...why cant we get a transpose that works cleanly,, ??
Just asking, not trying to be a wise assss,,,,,is it really that hard to move it cleanly a semi tone up or down without all the artifacts
I'll take a brief, although admittedly incomplete, stab at it. My goal is to mention a few of the issues that can lead to artifacts.
1. The output of a plucked string is analog and must be digitized(in most implementations) and quantized. Quantization can lead to accuracy issues.
2. Plucked strings generate a fundamental frequency plus harmonics. One could view the harmonics themselves as artifacts. This can create confusion in identifying the note the player intended to play. The fundamental plus the harmonics must ALL be transposed in the case of an ideal transposition. All of these frequencies must be discriminated and transposed accurately. If they are not, then there are artifacts.
3. The string can be bent so the guitar can generate frequencies that are not in the twelve tone row. The frequencies between the twelve tone row fundamental and the harmonics are infinite in theory. Each player squeezes out the notes in a slightly different way. Your C is slightly different than other guitarists and unique to your touch. This means infinitely precise recognition and generation of frequencies.
4. There are also transient properties as well that must be recreated as well. This can be the source of another set of artifacts. These change with the force used to pluck the string for instance. How long does the note sustain? The precision of the analog to digital conversion could a problem in regard to the transients. This can lead to more artifacts.
5. All these processes take time(latency). This is another artifact.
As mentioned, this is a non-trivial process to implement accurately.