Q: How do I put music from my iPod back on my computer after a crash

Did you fail to maintain a backup copy of your computer?

You can transfer itunes purchases from an ipod:  File>Devices>Transfer Purchases

This user tip should be helpful. It refers to the iPhone, but it's equally valid for iPods as well…

Syncing to a "New" Computer or replacing a "crashed" Hard Drive

See also Recover your iTunes library from your iPod or iOS device.

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