Vocal synthesis using sine: Difference between revisions

The easiest way to do FFT is using [https://tiusic.com/os_fft/deploy/index.html Liam's FFT tool]. Just upload a WAV file, choose a preset mode, and click GO. Then you can either copy the notes and paste them into a sequence, or download the sequence file and drag/drop it into OS. There are lots of advanced options to play with to optimize the output. This tool is based on the older fft.py script, which is now deprecated.  With the correct settings applied, it can use multiple copies of the 8 Bit Sine instrument to reproduce sounds more clearly than Jacob's FFT, but will generate hundreds of thousands of notes per minute.

This algorithm is highly effective at replicating the mid-to-high frequencies of an sound file, but depending on the chunking frequency in the Advanced Options panel, the lower frequencies will tend to be grainy and noisy, and will also lack clarity. A possible way to mitigate this limitation is to time-stretch your sound file using an audio editor, such as Audacity. Using the Effects tab found on the topmost panel, navigate to Pitch and Tempo (for Audacity versions 3.3+), then click on the Change Tempo option, while having the audio clip selected. Change the Beats per Minute field to "from 16 to 1" (either that or another power of 2 value such as 8-1 or 32-1, higher values give more frequency clarity, but will significantly inflate the note count). It's also essential to make sure that the high quality stretching checkbox is marked, otherwise Audacity will use the default algorithm of tempo-stretching, which is very low quality. The purpose of stretching the sound file is to allow more data for chunking in the FFT converter, which will increase frequency accuracy and also retain time accuracy. Return to the converter, open the time-stretched sound file, and divide both the minimum and maximum chunking frequency by the value which the audio has been time-stretched (e.g. 16). Run Liam's FFT converter, this time with the time-stretched audio file. Once it is finished, import the output *.sequence file into Online Sequencer and use the console to stretch the notes by a factor of 1/N, with N being the value used to time stretch the sound file. The resulting sequence should have clearer low frequencies, and less graininess or noise.