Furthermore, using Filters, or convolutions, also left me slightly wary. Why? because normal band, high or low pass convolution filters distort the signal.  Ok, it may not be much of a distortion, but it’s a departure from the original signal none the less.  During my first trials with the Fourier Transform I realised I could use the DFT and reverse DFT as a filter in the frequency domain, a rather expensive filter in terms of processing power, but a filter none the less that promised to keep true to the original signal.