This archive contains two utilities that let you work with  C64 .Tap files like the emulator CCS64 uses.  One of the utilities lets you create the .Tap files with the help of your sound card from .VOC files and the other will do conversion from .TAP to .VOC.  Docs are inside the archive.

This is a set of programs to manipulate Commodore 64 Datasette tape files. These tools can convert a WAV file to a TAP file and vice versa, or extract PRG/SEQ files from a TAP file. Additional tools are planned to convert PRG/SEQ files to a TAP file.

Although the screen shot makes this look like a DOS program, it will only run in a Windows CMD/DOS window.  Here is a description of the program straight from the readme file included in the archive:

This small tool belongs to the group of utilities supporting the emulation of the good old C64. To be more precise, it helps you to reuse your old tapes recorded with the C2N (Datasette) of  Commodore and full of programs for the C64. All you have to do is to record the C64-tape with your soundcard and your favourite sampling-software (for example the sound-recorder of Windows 9x).