The amber accord is one of the first accords that arose from the introductions of synthetics in the late eighteenhundreds. It was and still is one of the most important, most used accords in perfumery. And it is so simple! When you keep it basic it consists of vanillin and a labdanum extract and that is all. The formulation below is a good starting point, but you can change it any way you like.
Note that the formulation uses a 25% solution of vanillin and a 50% solution of labdanum resinoid. This means that a mixture of 2 drops of vanillin solution and 1 drop of labdanum resinoid solution consist of equal amounts of both (pure) fragrances! Formulating perfumes is a lot about calculating.
15 - Vanillin 25% in DPG
5 - Labdanum resinoid 50% in DPG
The real balance between vanillin and labdanum here is 15 x 0,25 to 5 x 0,50 = 3,75 to 2,5 = 3 to 2.
Though this ratio is a good starting point in general: any ratio between these two substances you can call an amber.