main.s

            TYP   $B3
            DSK   main.l

SPEAKER     EQU   $E0C030

HELLO       EQU   $8000
            ORG   HELLO
beep        LDA   SPEAKER
            LDY   #1000
            LDX   #1000
loop        DEX
            BNE   loop
            DEY
            BNE   beep
            RTL
            END

My assembly script:

#!/usr/bin/env bash
ls src/*.S | xargs ./bin/cadius INDENTFILE
ls src/*.S | xargs ./bin/merlin -V ./src/macro

sed -ie 's/Type(00)/Type(B3)/' src/_FileInformation.txt

./bin/cadius DELETEFILE blankdisk.po NEW.DISK/main
./bin/cadius ADDFILE blankdisk.po NEW.DISK src/main
gsplus

ok... $B3 is GS/OS Application which is an OMF file. Merlin(32) can create OMF file but needs the REL command, exits via a QuitGS call (instead of RTL) and the A/X/Y registers are 16-bit at entry, and there's no ORG (since it's RELocatable). Your code should work if you create it as a binary file with a auxtype of $8000 (the load address), use RTS instead of RTL and BRUN it from BASIC.