Thank you for 132!

Now for 131
Begins with

work out on the grid where the missing squares are for the 4 square battleship is and the two missing squares for the 3 square battleship is use the top row of the grid for the first coordinate Start from top down and going right, write down what the two letter coordinates are write down the 4 sets...

Sadly, I am completely stuck here. Looked at the spoilers and pressed the keys but can’t recognise any tune from this and don’t understand the first line of the written clue either, another spoiler please?

Got it thank you

Really really struggling here. Read all the spoilers. Just can’t work out whether this some form of arithmetic progression across the clues, some form of total movement or indeed how to express the answer.