1. C = 1 = dol

The key of C is Dol;

2, D=2=re

D key takes the sound of re as dol；;

3, E=3=mi

E is the sound of mi as dol；;

4, F=4=fa

F key is to use the sound of fa as dol.

if you want to find a tune on an instrument, the first task is to sing the scale 12345671 correctly and skillfully.

Take playing 1234567 on the piano as an example:

Play 1, 2, 3, 4, 5, 6 and 7 directly in C key.

key d should be played 2, 3, 4 (black keys), 5, 6, 7 and 1 (black keys).

Extended information:

Tone is determined by the vibration frequency of curved sound source. The greater the vibration frequency of the sound source, the higher the tone; The smaller the vibration frequency, the lower the pitch.

the first sound "1(do)" of different tunes has different frequencies.

for example, "1(do)" in C key has a vibration frequency of 256 Hz, and "1(do)" in D key has a vibration frequency of 288 Hz.

apart from the initial sound "1(do)", there are also "2(re)", "3(mi)", "4(fa)", "5(sol)", "6(la)" and "7(si)" in the tune in order.

Although they have their own frequencies, they all have a strict proportional relationship with the first sound "1" in frequency. This ratio between one sound and another is called an interval.

The first sound "1" of each tune has a certain frequency. According to the frequency of the first sound and the interval of each sound to the first sound, the frequencies of other sounds can be determined.

the frequency of "2" in C is equal to the frequency of "1" in D; The frequency of "3" in C is equal to the frequency of "1" in E, and so on.