Your sight is almost concise and to the point. Like any other languages, we receive their feelings with our ears. You might already have known that Japanese has 5 vowels, "a", "i", "u", "e" and "o". Depending on the vowel you see in the end of the phrase:
"i" and "e" = feminine
"a" and "o" = masculine
"u" = neutral
So, let's look at the words "yamete" and "yamero". The former ends with "(t)e" and the latter "(r)o". Then look at the list above. You'll see the former is feminine, the latter is masculine.
Masculine words are definitely masculine, but if you pronounce feminine words in high piercing voice, it will sound cold, greed and selfish.