Audio problem: When the kid shows El Mariachi how he plays, you can hear the part that he's not playing because it's a constant sound on one string and he's stroking all the strings at the same time.
Audio problem: When the bad guys in the car are shooting at Danny Trejo, the kid with the broken leg kills him with six shots we see and hear, but the slide on his gun locks back after 5.
Answer: It is called "Pass The Hatchet", and it is written by Ray Theriot, Roger Leon Jr. & Earl Stanley Oropeza. It was performed by Roger & The Gypsies. If you buy the soundtrack CD, it is on there, too.
Deezul