Two possible red herrings to mislead us :

1. The HTI has a tune Trumpet (but associated with different words) related to a set-piece version "Immortality" :
<<
7745 Trumpet 5(U1)1D76(5)6(7U1)1(D4)3(4)3(2) - 55(67)U1D7(U12)21(D7)65 - 7U123(21)D56(57)U1(2)1(D7) -

U1D6(7)U12(34)32(1)D7U1 - 111111D7U1 - 122D7U1211(D7) - U11D766U211(D7) - U13211433(2) - [312(3)443(2)1(D7)U1]
Meter: 8.8.8.8.8.8.8.8.0 Mode: major 2 citation s (2 in prototype sources) , earliest in 1799

‘Abridged from Dixon’. The original set piece has not been found in any collection by any Dixon, but it is found in later American collections such as AddiSVS as IMMORTALITY.

Source Date Region Tune No. Tune Name Text Attribution Key Voicing
HaweSSVAC 1799 e 7745 Trumpet WGROCS1 Dixon D 1/4
AddiSC 14 1805 e 7745 Trumpet WGROCS1 Dixon D 1/4
Total of 2 citations

WGROCS1 When God restored our captive state, joy was our song, and grace our theme
>>


2. A number of c.1800 hymn books contain a hymn like

"52 Death swallowed up in Victory
DIXON'S
WE sing his love who once was slain
Who soon o er death reviv d again
That all his saints thro him might have
Eternal conquests o er the grave

Soon shall the trumpet sound and we
Shall rise to immortality ....."

-often attributed to Rowland Hill's Surrey Chapel Collection (and one Dixon was a composer associated with the Surrey Chapel).
The Finsbury Chapel Collection of Hymns (texts) gives tunes for the hymn as
"TRUMPET Colesham 73 Staines 322" where
"The Tunes inserted at the head of the Hymns from Dr Rippon's Book are put in Italic letters to distinguish them from the tunes in the Companion The Hymns which have had regular pieces of Music set to them have the name of such pieces inserted in Capitals and those which are not found in Dr Rippon's or the Companion are either published singly by J Peck Newgate street or they are to be found in the Surrey Chapel Collection "

I don't know if any of this helps ! It might be handy to get more info on your Carribean Moravian anthem.

Tim