MIDI Notes

MIDI note numbers and Middle C definition.

Middle C is MIDI Note Number 60.

This can be C3 or C4, or even C2 or C5. There is no defined standard or convention. The MIDI standard only says that the note number 60 is a C, it does not say of which octave.

Ref.: Complete MIDI 1.0 Detailed Specification :

Each note is assigned a numeric value, which is transmitted with any Note-On/Off message. Middle C has a reference value of 60. This is the middle C of an 88 note piano-style keyboard though it need not be physically located in the center of a keyboard.

Other refs :

Notes on a piano: https://en.wikipedia.org/wiki/Piano_key_frequencies
What wikipedia says: https://en.wikipedia.org/wiki/C_(musical_note)#Middle_C

Octaves range depending on the definition of middle C:

With middle C defined as C3 :

MIDI note number	Note names (English)
127	G8
120	C8
60	C3 (middle C)
24	C0
0	C-2

With middle C defined as C4 :

MIDI note number	Note names (English)
127	G9
120	C9
60	C4 (middle C)
12	C0
0	C-1

All note numbers alongside key numbers of 61 and 88 notes piano keyboards:

With middle C defined as C4

Source

MIDI note number	Note name (english)	Frequency equal tuning at 440 Hz	Key number 61 keys organ	Key number 88 keys piano
127	G9	12543.85
126	F#9/Gb9	11839.82
125	F9	11175.30
124	E9	10548.08
123	D#9/Eb9	9956.06
122	D9	9397.27
121	C#9/Db9	8869.84
120	C9	8372.02
119	B8	7902.13
118	A#8/Bb8	7458.62
117	A8	7040.00
116	G#8/Ab8	6644.88
115	G8	6271.93
114	F#8/Gb8	5919.91
113	F8	5587.65
112	E8	5274.04
111	D#8/Eb8	4978.03
110	D8	4698.64
109	C#8/Db8	4434.92
MIDI note number	Note name (english)	Frequency equal tuning at 440 Hz	Key number 61 keys organ	Key number 88 keys piano
108	C8	4186.01		88
107	B7	3951.07		87
106	A#7/Bb7	3729.31		86
105	A7	3520.00		85
104	G#7/Ab7	3322.44		84
103	G7	3135.96		83
102	F#7/Gb7	2959.96		82
101	F7	2793.83		81
100	E7	2637.02		80
99	D#7/Eb7	2489.02		79
98	D7	2349.32		78
97	C#7/Db7	2217.46		77
96	C7	2093.00	61	76
95	B6	1975.53	60	75
94	A#6/Bb6	1864.66	59	74
93	A6	1760.00	58	73
92	G#6/Ab6	1661.22	57	72
91	G6	1567.98	56	71
90	F#6/Gb6	1479.98	55	70
89	F6	1396.91	54	69
88	E6	1318.51	53	68
87	D#6/Eb6	1244.51	52	67
86	D6	1174.66	51	66
85	C#6/Db6	1108.73	50	65
84	C6	1046.50	49	64
83	B5	987.77	48	63
82	A#5/Bb5	932.33	47	62
81	A5	880.00	46	61
80	G#5/Ab5	830.61	45	60
79	G5	783.99	44	59
78	F#5/Gb5	739.99	43	58
77	F5	698.46	42	57
76	E5	659.26	41	56
75	D#5/Eb5	622.25	40	55
74	D5	587.33	39	54
73	C#5/Db5	554.37	38	53
72	C5	523.25	37	52
MIDI note number	Note name (english)	Frequency equal tuning at 440 Hz	Key number 61 keys organ	Key number 88 keys piano
71	B4	493.88	36	51
70	A#4/Bb4	466.16	35	50
69	A4 concert pitch	440.00	34	49
68	G#4/Ab4	415.30	33	48
67	G4	392.00	32	47
66	F#4/Gb4	369.99	31	46
65	F4	349.23	30	45
64	E4	329.63	29	44
63	D#4/Eb4	311.13	28	43
62	D4	293.66	27	42
61	C#4/Db4	277.18	26	41
60	C4 (middle C)	261.63	25	40
59	B3	246.94	24	39
58	A#3/Bb3	233.08	23	38
57	A3	220.00	22	37
56	G#3/Ab3	207.65	21	36
55	G3	196.00	20	35
54	F#3/Gb3	185.00	19	34
53	F3	174.61	18	33
52	E3	164.81	17	32
51	D#3/Eb3	155.56	16	31
50	D3	146.83	15	30
49	C#3/Db3	138.59	14	29
48	C3	130.81	13	28
47	B2	123.47	12	27
46	A#2/Bb2	116.54	11	26
45	A2	110.00	10	25
44	G#2/Ab2	103.83	9	24
43	G2	98.00	8	23
42	F#2/Gb2	92.50	7	22
41	F2	87.31	6	21
40	E2	82.41	5	20
39	D#2/Eb2	77.78	4	19
38	D2	73.42	3	18
37	C#2/Db2	69.30	2	17
36	C2	65.41	1	16
MIDI note number	Note name (english)	Frequency equal tuning at 440 Hz	Key number 61 keys organ	Key number 88 keys piano
35	B1	61.74		15
34	A#1/Bb1	58.27		14
33	A1	55.00		13
32	G#1/Ab1	51.91		12
31	G1	49.00		11
30	F#1/Gb1	46.25		10
29	F1	43.65		9
28	E1	41.20		8
27	D#1/Eb1	38.89		7
26	D1	36.71		6
25	C#1/Db1	34.65		5
24	C1	32.70		4
23	B0	30.87		3
22	A#0/Bb0	29.14		2
21	A0	27.50		1
20	G#	25.96
19	G	24.50
18	F#	23.12
17	F	21.83
16	E	20.60
15	D#	19.45
14	D	18.35
13	C#	17.32
12	C0	16.35
11	B	15.43
10	A#	14.57
9	A	13.75
8	G#	12.98
7	G	12.25
6	F#	11.56
5	F	10.91
4	E	10.30
3	D#	9.72
2	D	9.18
1	C#	8.66
0	C-1	8.18
MIDI note number	Note name (english)	Frequency equal tuning at 440 Hz	Key number 61 keys organ	Key number 88 keys piano