# Music Key Incrementation

**URL:** <https://forum.makecode.com/t/music-key-incrementation/4556>\
**Category:** Help\
**Created:** [November 21, 2020, 11:05pm UTC](https://forum.makecode.com/t/music-key-incrementation/4556 "2020-11-21T23:05:26Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![GameGod](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/gamegod/32/2756_2.png) [@GameGod](https://forum.makecode.com/u/GameGod)\
**Post date:** [November 21, 2020, 11:05pm UTC](https://forum.makecode.com/t/music-key-incrementation/4556/1 "2020-11-21T23:05:26Z")

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I noticed each key is represented by a number. What is the incrementation or pattern of the numbers?

Ex:  
Low C = 131  
Low C# = 139  
etc.

These numbers pop up in the parameter area when you click on a key.

![image](https://us1.discourse-cdn.com/flex020/uploads/makecode/original/2X/e/e8fc41b3a86470b233669891c7366b7748d858f7.png)

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<div class="post-metadata">

**Author:** ![UnsignedArduino](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/unsignedarduino/32/592_2.png) [@UnsignedArduino](https://forum.makecode.com/u/UnsignedArduino)\
**Post date:** [November 21, 2020, 11:31pm UTC](https://forum.makecode.com/t/music-key-incrementation/4556/2 "2020-11-21T23:31:33Z")

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It’s the hertz of a note. There is a formula - you can search up “note name to hertz.”

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**Author:** ![jwunderl](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.makecode.com/jwunderl/32/5308_2.png) [@jwunderl](https://forum.makecode.com/u/jwunderl)\
**Post date:** [November 22, 2020, 12:04am UTC](https://forum.makecode.com/t/music-key-incrementation/4556/3 "2020-11-22T00:04:50Z")

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Yup, here’s the source code mapping for key -\> number:

> <https://github.com/microsoft/pxt/blob/349e5676a75934e603747f539db4015923ea2c91/pxtblocks/fields/field_note.ts#L531>