Warning - the first two sections are likely way out of date, as they were done many years ago when I had an old-school PC with a line-in socket, when these things were provided as standard. Today you'd need to get a device that would plug into a USB port. As for the utilities referenced, they may have been superseded by now. Certainly, the links no longer work and have been removed.
I connected the load/play socket on the tape recorder to the 'line in' socket on the PC, pressed the play button, then recorded each program as a sound file (of screeches and squawks!) using the PC with the following audio settings:
8 bits
44 KHz Sampling
Mono
In addition, I silenced the microphone input using the 'Volume' control in the System Tray.
Setting the correct playback level on the tape recorder when using the Spectrum originally was often difficult - if it wasn't just right, the program would fail to load. Luckily the level hadn't been changed since I last used the machine, and it required just a bit of fine tuning. I used the sampler utility in a program called TAPER, which has a visual representation of the signal being recorded, and this can be used to determine if the playback setting is too high or too low. (I was unable to use TAPER to record the sample, getting a message saying that the soundcard wasn't suitable). Anyway at the end of this stage, I had a VOC file for each of my programs.
The next steps were to use TAPER to check the source code and convert the files to a suitable format. What was interesting was that although most seemed to be corrupted in some way, I found I could load and run some of the seemingly corrupted ones into the WINZ80 emulator. It was thrilling to see those programs spring back into life after an interval of many years!
One program - the orbital simulation - was only partially available: a lot of lines towards the end were missing. Now I could just load the program, and key in the remainder, but the Spectrum never made editing very easy, although the realspectrum emulator does have a limited means of entering text using the keyboard characters rather than the coded keys. What I wanted to do was to dump the program to a text file and edit it under Windows, then re-import it. Well, I couldn't find a way of dumping the file, but I did come across a utility to enter text in an ASCII file, then convert it to a TAP image file. It is called bas2tap. All I then had to do was to use the MERGE statement on the Spectrum emulator to append the new text to the old program. In doing so, I even improved upon the old program - my first bit of Spectrum programming in the new millennium!
These were converted from voc files to TAP file format much much later (in 2022) using audio2tape, one of the Free Unix Spectrum Emulator* (Fuse) utilities:
audio2tape -t simple -s <source.voc> <source.tap>
I had a checksum error on one of the tapes and had to change the command by adding a new flag and tweaking the value by trial and error:
audio2tape -t simple -s -z 130 <source.voc> <source.tap>
For each assembly language program, a Fuse session was opened up with ZEUS Assembler running (freely available to download from here). Then the TAP file was loaded into Fuse (using Media, Tape options and then LOAD "" CODE in BASIC) for ZEUS.
* I installed Fuse on an Ubuntu system quite simply as follows:
sudo apt-get install fuse-emulator-gtk
sudo apt-get install spectrum-roms
sudo apt-get install fuse-emulator-utils