F#6 is F#, A#, C# and D# — F# with a major sixth added on top.
It sounds warm, and finished without being sweet. It closes a tune as firmly as the triad does but without the maj7’s shine, which is why so many standards end on one.
Tonic — an ending chord.

| F# | A# | C# | D# |
|---|---|---|---|
| 1 | 3 | 5 | 6 |
Also written F#maj6, F#M6 or F# major 6. The same chord either way; which spelling you meet depends on who wrote the chart.
F#6 in 6th in bass puts D# in the bass instead of F#, the 6th of the chord. The notes are the same; what changes is what the bass line does, which is most of why you would reach for it — it lets the lowest voice move by step where the root would have jumped.
One of F#6’s 10 common shapes does this:11-13-11-11-14-11
Play F#6 as a shell — root, third and seventh — and the spare string takes the 9 (G#) or the #11 (B#).
All 10 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
How you get to it. The turn that lands on F#6 is G#m7 to C#7 — the ii and the V of F# — and C#7 shares its third and seventh with G#m7, so the hand barely moves between them.
In which keys. Every note of F#6 belongs to C# major (the IV), Eb minor (the ♭III), F# major (the I), Ab minor (the ♭VII), Bb minor (the ♭VI) and B major (the V).
Every note of F#6 is in F# major pentatonic, F# major, F# lydian, F# mixolydian and F# lydian dominant.
Change one note of F#6 and you have F# (drop the sixth), F#maj7 (the sixth becomes the major seventh), F#m6 (the major third becomes the minor third), F#add9 (the sixth becomes the ninth), F#69 (add the ninth) or F#7 (the sixth becomes the flat seventh).
F#6 is a major chord — root, major third, fifth. Major chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.