I've noticed that a variety of pieces in the classical repetoire (certainly at least the piano repetoire), label what seems to be effectively the same key signature differently. That is, I am not aware of any differences in terms of key between a piece in "G Sharp major" and "A flat major" (or their equivalent minors). Is there any reason that sometimes a sharped key signature is used while at other times the equivalent flatted key signature is used?

As a related point, I have undoubtedly noticed the preference of certain "equivalent" key signatures over others. For example, one encounters "E flat" significantly more than "D sharp" and likewise "C sharp" significantly more than "D flat". Is there any particular reason for this, or is it simply a convention that has been handed down to use through musical history?


Question: What should I look for in a recording microphone for personal use?
Answer: There are two (popular) types of microphones: dynamic microphones and electret/condensor mics.

Dynamic microphones

They work like a speaker in reverse. Sound moves a diaphragm/coil assembly. The coil moves over a magnet and a current gets induces. Hence we have voltage.


Almost indestructible. YOu can literally pound nails with a Sure SM58
(fun abuse video here 
            
                
                    
                    
                    
                    
                    
                
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Very good at very loud sources, can be shoved in front of a Marshall stack without clipping
no inherent noise on their own
However, very low sensitivity. Need a LOT of amplification for low and medium level sources
They are almost always "Cardoid" or "supercardiods". This makes them more resilient against feedback but it also creates a lot of artificial bass amplification for sources that are close to the mic. They tend to make the voice very "boomy"
Frequency response is typically not very flat.


Electret or Condenser Microphones

They work by having a diaphragm moving against a statically charged electrode. Moving the diaphragm changes the electric capacity of the contraption which modulates the charge current. The current is super tiny so all microphone of these type have build in pre-amplifier that needs a power supply. This supply either comes from a battery, an external power supply box, 48V phantom supply from a mixer or interface box, or from the USB spigot. Electret are mostly omni directional but some are also cardioid or supercardiod or even switchable. We assume an omni here,


They tent to have a very flat frequency response, especially if it's an omni directional microphone.
Frequency response does not change with distance (no boomy voice)
Tend to have good sensitivity, good for low and medium level sources
Can clip at high volumes, so need to managed carefully
Has inherent noise in the capsule and the pre-amp. The larger the diaphragm, the smaller the noise
Fairly sensitive to feedback
Due to omni character more likely to pick up environmental noise


Because of the trade offs listed, most people use dynamic cardioid microphones in live situations and an omni-directional electret/condenser mic for recording. Electret are cleaner and truer to the original sound source but they need to be carefully managed in terms of placement, gain, noise, clipping, and external noise pick up.

Tip: if you are into DIY projects you can build your own with a very inexpensive electret capsule (such as the Panasonic WM-61A). See https://pantherfile.uwm.edu/type/www/audio-reports/PanasonicWM-61A_OtherBinauralRigs/WM61A_Webpage_Caps_Mounts.html. These can make remarkably good mics that sound as good as commercial micd that cost 100s of $.