Here's the breakdown:
* sto - The "o" in this part of the word is a short "o" sound, which is the schwa sound.
* mach - The "a" in this part of the word has the "ah" sound.
The schwa sound is a very common vowel sound in English, often represented by the letter "a" but can also be represented by other vowels like "e", "i", "o", and "u" depending on the word. It's the "uh" sound you hear in words like "about", "again", and "the".