A library to get frequencies from pitch names. Mainly:

NoteFrequencies.frequency_from_name("e'") # => 326.93

The naming accepts both Helmholtz (middle C is c') and scientific notacion (middle C is c4).

Alterations accepted include Lilypond’s style (es, is, eses, isis) and ASCII style (b, #, bb, ##, x).


Add this line to your application's Gemfile:

gem 'note_frequencies'

And then execute:

$ bundle

Or install it yourself as:

$ gem install note_frequencies


To get the frequency from a named note:

NoteFrequencies.frequency_from_name("e'") # => 326.93

To get the frequency from a delta (from middle A)

NoteFrequencies.frequency_from_delta(-5) # => 326.93

Fork tuning is configurable:

NoteFrequencies.frequency_from_name("a", :tuning => 443) # => 221.5

Frequencies are rounded by default to 2 decimal places. Should you need more precission:

NoteFrequencies.frequency_from_name("e'", :round => 5) # => 329.62756 

Both scientific notation and Helmholtz’s notation are accepted:

NoteFrequencies.frequency_from_name("a4") # => 440.0
NoteFrequencies.frequency_from_name("a'") # => 440.0

Alterations are accepted as b (flat), bb (double flat), es (flat), eses (double flat), # (sharp), ## (double sharp), x (double sharp), is (sharp) and isis (double sharp).


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request