Video footage from the HV20 will be fine if you:
1) capture the video under good lighting conditions. NO low-light.
2) ALWAYS use some sort of stabilizing device. Chair, table, tripod, SpiderBrace type shoulder-mount device... NEVER handheld.
3) Learn to use the white balance feature. And use it. This is critical if you have indoor shots.
4) When shooting indoors, turn on the lights. Did I mention you need to be capturing under GOOD lighting conditions and NOT under any lowlight conditions? ; )
5) Use the manual audio control. While you should not be using the audio captured by the camcorder during the video capture, help your self and use the manual audio control. It will be easier to sync. If the camera is moving, then the sound-field will move.
6) Record the audio first and play-back and lip sync. DO NOT move the camera. This will keep the sound-field stable.
7) record MULTIPLE times... even if you think you got it right, do it again. and again. and again.
8) when in manual audio, never allow the meter past about 3/4.
9) There are two ways to do "slow motion" One way is realtime during capture... open the shutter really wide when recording. The audio will stay in sync and movement will be "ghosted". The other way is to take a clip and slow it down with the editor. This is OK for "b-roll" fill-in. If you do the latter, you will get a better image if the shutter is REALLY fast. Play with the camcorder and those settings to see if they give you what you want.
10) Do not go in "cold" and expect you will have the best video to deal with. Use the camcorder a LOT for about a month to understand what it can - and cannot - do and understand the whole process - including uploading to your computer and editing - and playing with the features the editor has.
11) Plan, plan, plan. Storyboard your shoot. Get the lyrics to the song and draw what the camera should see during the different points of the song - and set up the shots. Use a shot list and be sure you get all you need/want.
12) I think you should know that you need to be capturing under GOOD lighting conditions and NOT under any lowlight conditions? ; )
13) If you must pan, pan s l o w l y. Better yet, don't pan or pan REAL fast and only expect to use a fraction of a second as a short insert/cutaway.
14) If you must zoom, zoom s l o w l y. Better yet, don't zoom or zoom REAL fast and only expect to use a fraction of a second as a short insert/cutaway.
15) Watch some music videos on MTV, YouTube, VH1 or whatever... Don't know what kind of music your band does, but check the clip lengths on those video sources... generally speaking, it lasts around 2 seconds. So... on a 3 minute song... that is 180 seconds divided by 2 seconds per cut = ~90 cuts to make the video.
16) TURN ON THE LIGHTS.
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Just so there is a frame of reference - you want to do a "professional music video" with equipment most professionals would not use. The HV20 is a$600-$800 camcorder with a 43mm lens and a small imaging chip. A "professional" will be using something from the Sony HVR series, Canon XH or XLH series, the Panasonic DVX or HDX series or the JVC GY series.
That said, compelling content will trump equipment quality nearly every time... Make it interesting, and if the song is good, and the video captured is edited well, the camcorder you use will have little bearing on the success of your video.