Guitar Effects Pitch Scaling
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Conclusions This project has demonstrated the usefulness of digital signal processing in the area of guitar effects and processes. Digital offers many advantages over analogue devices in the form of improved signal quality, lower power dissipation and increased effect per device ratio. A large worldwide market also gives added incentive for the development of useful digital applications. The first major part of this project dealt with effects creation and implementation in real time on a DSP unit. Effects such as distortion, wah wah and reverb all have their origins in analogue form. The point of this part was to transfer them into the digital domain where the benefits of digital can be explored. A wide range of variables have been identified, that allow the guitarist a huge variation in sounds from the effects. Sometimes these variables are best changed in a preset form, taking away much of the complexity of finding a good sound. The effects, while complete in their design, need to be refined to be able to be chained together in a final product implementation. The second major part looked at implementing a pitch-scaling algorithm to replace the need for a capo device. The ‘electronic capo’ allows the guitarist more freedom in their playing, and increases the frequency range of the guitar by at least +/-5 semitones. Pitch scaling devices are not commonplace in the guitar market. A few are available but at a typical cost of $150 US. That sort device does only scaling, and if effects want to be used at the same time, a separate unit needs to be chained to the output of the scaler. Therefore, a device that has multiple guitar effects, as well as a pitch scaling process in one unit, at a reasonable price is a valuable tool for a guitarist. Initially, an FFT approach was investigated, but because of memory limitations and excessive delays, the synchronous overlap and add method was investigated fully. This time domain based approach resulted in excellent quality results with guitar signals, with a wide range of semitone variations. The DSP implementation has been successful and the processing delay is unnoticeable. |
