Can I use a microsd card on my surface as the primary source for itunes.

Yep, move the whole iTunes folder, then shift-start-iTunes to connect to the iTunes Library.itl file inside it from the new path. This assumes that the library is in the standard shape with all media inside the iTunes Media folder which in turn is inside your main iTunes folder. The user tip explains how to manipulate the library into this layout if required.

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Apple's 6 pages of exhaustively meticulous step-by-step instructions: How to move your iTunes library to a new computer - https://support.apple.com/HT204318 Use this if you suspect any of your media are not in the standard location (iTunes Media folder).

My one-sentence summary if you always use iTunes' default preferences settings: Copy the entire iTunes folder (and in doing so all its sub-folders and files) intact to the other drive, hold down the option/alt key (shift on Windows) while starting iTunes, and when requested to select a library select the iTunes Library.itl file in the copied folder (Open a different iTunes Library file or create a new one - https://support.apple.com/HT201596).

See Make a split library portable. Assuming the MicroSD card is large enough for your library there is no reason why you cannot store it there.

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