FRQEditor is a tool created by nmasao for editing frequency map files created by various UTAU resamplers, which can run as an UTAU plugin or a standalone application. It can also be used to generate files for entire voicebanks, or convert the files between formats.
Official release: Twitter
Direct download: MediaFire
Voicebanks may have frequency maps in only one format, which were generated with more accurate tools or manually corrected. If you regenerate files from scratch with another resampler, they may have errors or glitches. Instead, convert the original format to the format you need.