Theory
If you got your first "boom!" on open E yesterday, you're halfway there. Slap isn't fingers, it's a drum — remember, the thumb is the kick, the ghost note is the rest that fills the gap. Today you add two things — slapping across strings (E↔A) and slap's real hurdle, muting (silencing the strings you don't play). Only when these two join does the thumb turn from "practice" into "groove."
Moving strings is easier than it looks. The forearm rotation stays exactly as yesterday; only the target string changes. Open E is the 4th string, open A is the 3rd string just above it. Keep the wrist still, shift the thumb inward by one string, and slap at the same angle — A booms just the same. Don't swing the whole forearm; the trick is to keep the thumb's travel distance minimal.
But slap is loud and full of open strings, so left alone, even the strings you didn't play ring out and get muddy. That's why muting is essential. The left hand lays fingers flat and rests lightly on the unused strings to deaden them, while the right thumb covers the strings lower than the one you're playing. Both hands must guard like gatekeepers so only one note stays clear. Add a pitchless ghost note ("chick") in between, and the silence itself becomes rhythm — it's marked as X on the score.
On a 5-string there's one more string to deaden. Keep the thumb over the low B so it never rings out while you move between E and A. The E·A positions are exactly the same as on a 4-string, so a 5-string just asks for a little more muting care.
See it
Today you see three examples. First check the E and A spots on the fretboard, then move across the two strings with the thumb, and finally learn muting with a ghost note. Each example comes in both a 4-string and a 5-string version.
First, the E·A thumb strike map. The two blue dots are open E (4th string) and open A (3rd string).
▶ 4-string. The lower blue dot is open E (4th string), the upper blue is open A (3rd string). Shift the thumb by one string and slap at the same angle.
▶ 5-string. The E·A spots are the same as on a 4-string. Rest the thumb on the low B to keep it deadened as you move between the two.
Example 1 — thumb string change E↔A. Slap open E and open A alternately. The thumb travels the shortest distance between the two strings.
▶ BPM 60, 4-string. Alternate open E (4th string) → open A (3rd string) with the thumb. Check by ear that both "boom"s are equal in size.
▶ BPM 60, 5-string. Same note and position as the 4-string. Rest the thumb on the low B so it doesn't ring out while moving.
Example 2 — thumb + ghost. Alternate an open E thumb slap with a ghost note (X). The clearer the silence of "boom-chick-boom-chick", the more the groove comes alive.
▶ BPM 65, 4-string. On the beat, a blue open E thumb slap; off the beat, X (chick). The bigger the size gap between thumb and ghost, the clearer the rhythm.
▶ BPM 65, 5-string. Same notes as the 4-string. Keep the thumb over the low B so it doesn't ring along even when you play the ghost.
Today's practice
0–10 min · Warm-up Loosen up yesterday's open E thumb slap at BPM 60. First check whether the "boom" tone is as even as yesterday.
10–20 min · Brain training Move very slowly between open E and A. Focus only on whether the thumb shifts by just one string — that minimal travel.
20–40 min · Real play Repeat Example 1 (E↔A move) at BPM 60 → once both "boom"s are even, move to Example 2 (thumb + ghost) at BPM 65. If unplayed strings ring out, go back to Example 1.
40–50 min · Record/feedback Record 30 seconds and listen for whether only the played string rings and the rest stay silent. Note the BPM you reached today.
Done when: you can move between open E and A with the thumb at 60–65 with both "boom"s even, and the unplayed strings staying quiet.
- The thumb moves too much. If the thumb flies far when crossing strings, the beat drags. Shift it by just one string, minimally.
- Unplayed strings ring out. If A·D·G ring while you play E, lay the left hand lightly over those strings to deaden them.
- Ghost note too hard. Hitting the chick too hard revives the pitch and gets messy. Very lightly, only the muted attack sound.
- Neglecting low B (5-string). If you lose B while focused on string changes, the low end leaks. Always keep the thumb resting over B.