आस्य is उच्चारण स्थान. The प्रयत्न of the उच्चारण स्थान of comparable (similar) letters would be the same (dominant letter).
All दीर्घ सन्धि are examples of this.
प्रयत्न are of two types :
आभ्यन्तर and बाह्य
आभ्यन्तर in turn is classified into 5 sub-types:
1. स्पृष्ट - from स्पर्श- word for clear in Sans/Hindi. The tongue completely contacts the particular part of the mouth.
2. ईषस्पृष्ट - The tongue only partially contacts the particular part of the mouth e.g. in य् र् ल् व्
3. ईषद्विवृत - The throat stays "somewhat" opened in this type of प्रयत्न. ऊष्म letters: श् ष् स् ह् are examples of this प्रयत्न
4. विवृत - In this प्रयत्न the mouth stays open but the tongue is relatively free.
5. संवृत - In this प्रयत्न the mouth stays open but the tongue isn't free (only अ )
बाह्य is of 11 types
1. विवार - The mouth clearly opens
2. संवार - mouth is only partly opened
3. श्वास - breath is used
4. नाद - long sound
5. घोष - echo or repetition
6. अघोष - without any echo
7. अल्पप्राण- the pronunciation that requires very little breath/energy
8. महाप्राण - the pronunciation that requires a lot of breath/energy
9. उदात्त
10. अनुदात्त
11. स्वरित