We now cut high fidelity 78rpm custom vinyl records on our lathe by using the half speed mastering technique.
Half speed mastering on a basic level is exactly that the recording and the lathe are running at half speed well not quite half speed in this case. The 78rpm recording is cut at 45rpm but the audio is slowed down sufficiently so when played back on a 78rpm turntable the audio sounds normal and plays back at the right speed.
Why bother with half speed mastering at all as you can imagine there really is no point in listening to the audio as it is being cut, because it is playing back at half its speed and sounds terrible. This also takes a lot more time to create a record as it is cutting at half speed so taking twice as long to cut. Also any processing normally done while mastering to disc has to be done beforehand such as eq, compression and De-essing so this adds to the length of time it takes to produce your custom 78rpm vinyl record.
What makes this so worthwhile is that while cutting at half speed, the lathe cutting head has more time to create the groove and allows more information to be cut to the record much more detail is captured the highs are brighter the sound is clearer than usual on vinyl half speed cutting basically gives you HD Vinyl with no wavering or at least much less on long notes as the cutter head has more time to process the audio information.
Cutting at half speed means that the information that is within the recording the frequency is halved by half speed cutting 16khz will be 8khz while cutting enabling for much more detailed high freq response on playback. Cutting at half speed puts much less stress on the cutterhead and amplifier resulting in a louder cut with more definition deeper bass and increased stereo imaging.