https://www.musical-u.com/learn/how-to-learn-to-spell-intervals-fast/
Being able to quickly spell intervals quickly is essential for ear training.
Learning to recognise intervals develop a musical ear. It is also fantastic brain training. This means learning to “spell” the intervals with correct note names.
This can seem like a huge task at first. In this article we share some handy shortcuts to accelerate the process.
https://www.musical-u.com/learn/how-to-learn-to-spell-intervals-fast/