microphones broadly fall into 2 distinct types
- Condenser - requires a power source either a battery inside the microphone itself or remote 'phantom power' usually provided from a p.a. mixer.
- Dynamic - do not require a power source. Most famous of all is the Shure SM57 (instrument / vocals) and SM58 (lead vocals) used by many musicians and singers around the world.
Condenser microphones are used extensively in recording studios because they are very sensitive and have a better range than dynamic mics. However they are a bit fragile and good ones are expensive. There are plenty of cheap condenser microphones about but they give a rather tinny sound.
If you want the microphones for general band work, especially gigging you will get better value for money with dynamic microphones. These are much less sensitive that condenser mics and are intended for close up work - no more than a few inches from the mouth of the singer (use a pop shield to prevent unwanted noises) or hung close in to an instrument.
There are also 3 different pick-up patterns for microphones. Which ones you go for will depend on the use for which they are intended.
- Cardoid - cone shaped directional pick up pattern. These will only pick up sound from in front of the microphone in a cone shape of about 60 degrees. Suitable for general vocals and instruments. Good resistance to feedback. To effectively mic-up a big instrument like a piano you may need to use more than one mic.
- Hyper Cardoid - as above but with a much narrower pic-up sone - a cone of about 30 degrees. These are very good for lead vocals as you can drive them a bit harder without risk of feedback or picking up other instrument sounds on the stage (particularly useful if you have a singer who plays an a loud acoustic instrument or a keyboard with built in speakers). THese are okay for using to mike-up an instrument where the sound comes from a small fixed point (saxophone, violin, trumpet, acoustic guitar - provided that the musician stands still) but not much good for larger instruments like pianos or harps. They are also good for mike-ing guitar amps, but only if they don't have a separate tweeter.
- Omni-Directional . These will pick up sound from all around. Whilst they can be good for picking up large acoustic instruments or choirs they are very prone to feedback and are not really suitable for public address purposes.
Don't be tempted to buy cheap microphones with permanently fitted cables, especially ones with a standard 6mm jack-plug. Always go for mikes with a balanced (3 pin xlr) cable as they do not pick up as much radio interference on the cable (but only provided your mixer/amp also has balanced inputs too).
Although many professionals swear by the Shure SM57 and SM58 mics mentioned above I personally prefer the AKG D55 a hyper-cardoid which has a longer pick-up range and higher output than the Shures (useful if musicians or singers hang back a bit from the mic) and usually slightly cheaper too. It is really good for lead vocals but makes a good instrument mic too with a nice crisp but warm sound across the frequency range.
For larger instruments, or two backing singers sharing a mike, I use the standard cardoid version of the same AKG (but I'm afraid I can't remember the model number now).
If you want to mike up drums that is another subject all together.