I play moderate level guitar in church. In relation to the numbering system for musical notes, I have seen in songs showing the chord changes, there would be an E2 or an A2 chord along with an E or A chord. Are they considered the same chord with no difference?
An "E2" or "A2" chord most probably means an "add 2" chord, where a major second note is added between the root and third of the chord. For example, E2 might be played like: 024100. Add2 chords are often used in so-called "praise & worship" music. Maybe even so often that someone might consider it a cliché, but hey, genres are made of clichés.
Edit: as Tim says, it might also mean a sus 2 chord. "Sus" means suspended, kind of like hiding the minor/major nature i.e. the third of the chord from the listener. The most common sus chord is a sus4, but other types are sometimes used as well. "Asus" (the chord, not the Taiwanese electronics company) alone means Asus4.
E2 seems a vague way to name a chord. Could be construed as piiperi says, which ought to be called Eadd2, or, it could be Esus2, where the M3 of E is replaced by the 2nd note ( F♯).
If there were some E4 chords also I'd consider they could be Esus4, where the M3 is replaced with the P4 (A).
Whether it actually means add2 or sus2, there's the second note (F♯ here) included. 'Add2' means the G♯ stays, 'sus2' means it gets left out.
Given the ambiguity in the naming, best to try each, and then decide. Or look at any available dots to determine.
E2 is what I’ll consider a problematic chord spelling that has been sooooo commonly seen until it’s become acceptable.
- Esus2: E F# B, the 3rd (G#) is replaced by a major 2nd
- Eadd9: E G# B + F#, a major triad extended by adding a major 9th (3rd is still present)
- E9: E G# B D + F#, this is a dominant chord, ie the dominant 7 (D) MUST be present
In my opinion and based on my observation, “E2” is usually a problematic chord spelling when it really means Eadd9 but specifically wants the added tone in closed voicings. But as you see above, it could give rise to confusions.
By the way it should be noted that chord spelling usually do not dictate how the notes in the chord are voiced (ie how the notes are arranged in different octave/registers) - it only defines what the root note is and what are the chord tones that must or must not be included or omitted.