selecting only first record meeting a criteria

Hi to all!

Database tables

Masters

 Reference

 Events

 inside a the Events Table I have this formula:

let xEvent := Event;
let xDate := Date;
let x := (select Reference where Date = xDate and Event = xEvent);
for i in x do
let y := (select Masters where 'Master Release Code' = i.'Master Release Code');
for j in y do
html(---  <span style="color: #191970">{ i.Track } </span></br>
<span style="color: #191970">{ j.'Master Release' } </span></br>
<img src="{ y.coverimage }" style="width: 60px; height: 60px; margin-right: 5px;"></br>  ---)
end
end

that shows this output:

as you can see the tracks are duplicated and in order to avoid this I am trying:

let xEvent := Event;
let xDate := Date;
let x := (select Reference where Date = xDate and Event = xEvent);
let previousTracks := [];
for i in x do
    let track := i.Track;
    if not contains(previousTracks, track) then
        let y := (select Masters where 'Master Release Code' = i.'Master Release Code');
        for j in y do
            previousTracks := previousTracks + track;
            html(---
                <span style="color: #191970">{ track } </span></br>
                <span style="color: #191970">{ j.'Master Release' } </span></br>
                <img src="{ y.coverimage }" style="width: 60px; height: 60px; margin-right: 5px;"></br>
            ---)
        end
    end
end

but it doesn't help....

any suggestions? thank you for the attention