Wrong notes in start/play melody

[martinwork]

Describe the bug

Arising from https://www.reddit.com/r/microbit/comments/1gsly00/does_anyone_else_have_this_bug_where_it_plays/

Wrong notes can be heard in start/play melody in both simulator and hardware.

It seems to have changed between v4 and v5. Both old "start" and new "play" blocks are affected.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://makecode.microbit.org/v4
2. Import https://makecode.microbit.org/_XmJJ4ab224b1
3. Press A to hear melody - seems OK
4. Try the same in v5, v6 or v7
5. Hear incorrect beep towards the end
6. Try v6 project in v6 or v7 https://makecode.microbit.org/_MKzbqwKCgAEg
7. Hear error

Expected behavior
No wrong notes.

micro:bit version (please complete the following information):
V1 and V2

Desktop (please complete the following information):

• OS: [e.g. iOS] Windows 10
• Browser [e.g. chrome, safari] Chrome
• Version [e.g. 22] 130

Smartphone (please complete the following information):

• Device: [e.g. iPhone6] iPad
• OS: [e.g. iOS8.1] iPadOS 18
• Browser [e.g. stock browser, safari] Chrome
• Version [e.g. 22]

[abchatra]

@riknoll fyi

[martinwork]

Changing 23 to 24 in this calculation fixes the built in melodies

pxt-microbit/libs/core/music.ts

Line 673 in d1c862a

octave = Math.idiv((melody[i] - 23), 12)

The octave for each B (e.g. MIDI 0x53) is currently calculated to be the same as the C above it (e.g. MIDI 0x54)

So Melodies.Entertainer:
4a014b014c0154024c0154024c0154035401560157015801540156015802530156025404
has a b5 near the end
['d4:1','d#','e','c5:2','e4:1','c5:2','e4:1','c5:3','c:1','d','d#','e','c','d','e:2','b:1','d:2','c:4']
that should be a b4
['d4:1','d#','e','c5:2','e4:1','c5:2','e4:1','c5:3','c:1','d','d#','e','c','d','e:2','b4:1','d5:2','c:4']
as in MakeCode v4

pxt-microbit/libs/core/melodies.ts

Line 78 in f349eef

return ['d4:1', 'd#', 'e', 'c5:2', 'e4:1', 'c5:2', 'e4:1', 'c5:3', 'c:1', 'd', 'd#', 'e', 'c', 'd', 'e:2', 'b4:1', 'd5:2', 'c:4'];

In the frequency calculation, octaves 1-8 are supported with note numbers C=1 to B=12

pxt-microbit/libs/core/music.ts

Line 548 in d1c862a

* @param octave The octave of the note (1 - 8)

The lowest supported note is c1 = MIDI 0x24=36. In fact I think b0 works, because it's note 12. . . 12 + (12 * (0 - 1))) = 0

Test: https://makecode.microbit.org/_8WmDKaLyqAax