So you may actually have 2 (or more) problems to solve here. To do it completely right probably costs more than $400, but gets you coverage for more areas, but you can also pick and choose problems to solve as long as your conscious of the compromises you're making and risks you're taking.
RAID 1 will copy the same bits to both drives, but if the file system gets corrupted or the file gets corrupted other than by the physical drive itself, that corruption will be on both drives. RAID won't help with Crypto locker or accidental file deletion either. A RAID capable enclosure will generally require external power as well.
RAID is probably common in music production for both speed and uptime. SSDs have/can change the game on the speed side while being more reliable than a standalone HDD as well. A single SSD is going to be faster than any sort of HDD based RAID array that's reasonably portable with a laptop (I'd consider even the 4 bay USB3.0 enclosures pushing the portability boundary). RAID 1 isn't any faster than a single drive (the same data gets written to both drives). RAID 0 is too risky for data you care about (any drive in the array failing loses 100% of the array's data). A good backup routine mitigates the amount of work you lose in the event of drive failure.
For >1TB music and video file storage for editing (compressed file playback is more or less trivial) you can put together a 2TB SSD in a USB 3.0 UASP enclosure.
Micron 2TB Drive for $285
Example enclosure, key specs are 2.5" drive, USB 3.0 and UASP
Pros: Fast, no moving parts, bus powered (no additional power supply), smaller size than a 3.5" drive
Cons: Price, max capacity
If the cost is too high, you can get bus powered 2.5" USB HDDs up to at least 4TB these days.
WD 4TB for $100
Then you need a backup device. For this I'd suggest 1 or more 3.5" high capacity USB 3.0 HDDs (alternating between 2 decreases the risk of a backup device failing when you need to restore the data). You can use a backup program to keep a number of full(everything on the drive) and differential (just what's changed since last backup) backups to restore from in the event of accidental deletion or wanting an earlier version of a file.
3.5" drives require external power, but you should only need the backup drive 1x day or 1x week depending on your work cycles and/or dataloss paranoia.
ex:
WD 8TB USB 3 for $160
If you're going with the alternating pair of backup drives, it's better to keep one of the drives at a different location if possible and then swap out the offsite drive after you take a fresh backup.
The higher price, higher functionality version of this would be to get a NAS device. Here's where RAID can come back into play depending on your total storage and archival needs. I've linked a 2 bay, you'd need to add 2x4TB or 2x8TB 3.5" HDDs from the vendor approved list to the NAS and configure for RAID1 (mirroring). This would net you 4TB usable from 2x4TB drives or 8TB usable from 2x8TB drives. Doubles your cost per TB, but saves your backups in the event of a single disk failure.
Larger NAS units are available and scale up in price based on drive bay capacity and NAS power/feature set. If you step up to a larger NAS, you can use single or double parity RAID configs (RAID 5 and RAID 6 and proprietary variants). RAID 5 gets you N-1 drives worth of capacity from N drives and can rebuild itself when a single failed drive is replaced. RAID 6 gets you N-2 capacity from N drives and can withstand concurrent failure of 2 drives.
Synology 2 Bay $170
Supported drives list filtered to NAS class drives (skipping enterprise as overkill for a 2 bay setup and desktop as not enough cheaper than NAS class drives generally.
TLDR: Trusting any single drive (or even enclosure) is risky. Using a separate working drive and cold or network backup solution can help protect your data.
