# Question for musicians (or physicists)

#### Anyee

##### Diabloii.Net Member
Question for musicians (or physicists)

I've been googling for this, but with no luck, so I'm turning to the OTF. How many hertz are in a semitone, i.e. C to C#?

#### publius

##### Diabloii.Net Member
I actually derived it with a couple of other people. A middle C is about 262 Hz. A note above middle C's frequency is 262*2^(x/12), where x is the number of half-steps above C.

So for example C# is one half-step above C, so its frequency is 262*2^(1/12), or about 278.

Edit: whoops, I forgot that we were deriving it for my B flat trumpet, 262 is actually B flat. So normally, a C is 278, a C# is 278*2^(1/12) or about 294 (it works the same, just one step higher).

#### Anyee

##### Diabloii.Net Member
Hrm, so in the range of 28 Hz. Use A, though. Better waveform. My tuner's at my gf's house and it allows minute changes in Hz.

#### Steel_Avatar

##### Diabloii.Net Member
It depends on the octave.

Here you go:

freq = base*2(x/12)

Base is any base frequency. Generally, A = 440 Hz is the accepted frequency. From here, X is the relative position of the note, going up. You can't go down. In your case Anyee, choose a base C, say 523.25 Hz (same octave as our A). C# is one position up, relative to C. Toss that into your calculator, and away you go.