I would like to practice only on some specific characters and then resume studying with the koch method.
I'm learning the letter "w" but I would like to hear it together with 2 or 3 other letters, how can I do?
You can also select CUSTOM character set in MorseMachine (after checking the characters you want in "Change CW settings"). I use it to torment my brain with the pairs of characters that I notoriously confuse (like "5" with "H" and "6" with "B") before doing another Koch lesson. And it helps.