Your query might refer to two types of video:
(1) What shows on Hauptwerk's console screen – virtual keyboards moving, virtual stops being activated, swell pedals moving etc. An example of this sort of video would be:
https://www.youtube.com/watch?v=XV2B4lHfsncI have a feeling that special software exists to make such videos; you could try sending a private message to the maker of one of them – in this case Piotr Grabowski, whose forum name is puciak. Make sure you are logged in to this Hauptwerk forum, then click on puciak's name within this discussion:
viewtopic.php?f=6&t=16613This will take you to his forum profile, and from there you can send him a message. I think Milan Digital Audio themselves must also be using appropriate software for their demos, e.g.
https://www.youtube.com/watch?v=DYXEmn1YwB0so you could try sending a query direct to Brett Milan. I believe this topic has already been discussed on this Forum, but I have not been able to find that discussion.
(2) The second type of video shows an organist playing a Hauptwerk sample set along with the Hauptwerk audio. An example of this type would be:
https://www.youtube.com/watch?v=leyAp_EdIjUIn that case you can record the video and sound using your camera, and simultaneously record the sound alone. You could use Hauptwerk's built-in recorder for this, or a separate digital recorder such as the Zoom H4n Pro, which can accept external microphones. There is specialised software to synchronise the audio and video, such as PluralEyes
https://www.redgiant.com/products/pluraleyes/This costs $299, but does give professional quality results. This type of software actually synchronises the separately recorded audio with that recorded by the camera; this means the video is automatically synchronised as well.
A page which discusses cheaper solutions is:
http://thinkinghard.com/blog/HowToSyncV ... Audio.htmlIf that does not solve the problem try a search for “software to synchronise video and audio”.
If your camera has an audio input by all means try that, but you may be disappointed by the sound. Most cameras give priority to image quality; audio can be an afterthought. Sometimes the sound is only recorded in mono; and you may find that audio is affected by automatic gain control, which many cameras apply to avoid fluctuations in level.
Hauptwerk's built-in recorder records directly from the soundcard, so you are guaranteed excellent quality. However if you have a multi-channel system, you will need to record via microphones to preserve the effect of sounds mixing in the air. This is a controversial topic, but to me multi-channel sound is much more realistic and alive. Good luck!