The best way to get Super Sentai music is through websites that ship from Japan. The cost of overseas shipping isn't as bad when it's a small disk capable of being held in a small bubble-wrap container.
The music I've primarily collected so far is from Samurai Sentai Shinkenger.
These two sites are good places to find Super Sentai Music.
- I usually use Play-Asia because they have low shipping cost, usually under $5.
- CDJapan is good as well, as they feature a link to listen to snipits of each song on the CDs, giving you certainty of what you're buying.
Now, when searching these sites the best trick is to select Music Only as a search, and then enter the title of the series you're looking for. (In this case "Shinkenger", or "Gekiranger" or any other Sentai series.)
OK, now to find the most appropriate CD you're looking for, look for the CDs around $20 to $30. Anything at $12, or features some add-on toy or booklet probably only has a few songs. For the actual Insert Songs you need to look at the CDs with 11 or more songs on a single disk. There are several versions of these CDs, in volumes.
Also - when searching for Super Sentai Music, bear this in mind: you'll probably have to wait for the CDs to come out. And, if you're only really interested in the Insert Songs, you'll most likely want to wait for the second volume of the CD series. When I got Shinkenger Hiden Onban Vol 2, it featured all of the Insert Songs up to that point and many new songs. No Background music.
If you're like me, you might only want Insert Songs.
Now, the the Hiden Onban Vol 2 CD only came out on July 29th. That's FIVE months before a proper CD is released. Before that Volume 1 is only Background Music, and there is the Shinkenger Single CD, which only has the opening and closing songs and karaoke versions of those songs. So be warned - you probably won't be able to get all the music of any new Super Sentai series right when the series begins. Give it time, and check Volume 2 for the Insert Songs.
Also - you have to keep in mind that each volume of the CD series will probably always have the Opening and Closing Music. So if you buy the first CD of a series, you might be getting less value with something like Volume 2 - which will have those songs and more.
Keep this in mind as well, that there are usually vocal tracks featuring the actors talking. This is essentially useless for anyone who doesn't speak Japanese - so keep that in mind when you see 19 Music Tracks, that might only amount to 11 actual songs. Like the opening and closing, some songs might repeat on other volumes.
UPDATE: I thought I had this all figured out - but it turns out Volume 4 and 5 of Shinkenger CDs is all instrumental music. Not a single legitimate vocal track. I am so disappointed. For anyone looking to avoid the instrumental music - Volume 2 is it. That's the CD with the most Insert Songs, as far as I can tell.
2ed UPDATE: The final Shinkenger CD came out, called Zenkyokushu. It finally had what I was looking for, all of the vocal tracks from the series, character songs, and including music from the Shinkenger vs Go-onger movie. So, lesson learned here - you can get the best deal for your money if you wait until the series music you want has finished it's run on the air. I know, it's a long wait, though. Now I want Goseiger music.
Enough of me blathering on - see for yourself. Here are the links to the Shinkenger Music CDs. Under Tracklisting you can click to listen to samples from each CD.
I hope this might help anyone who might be interested in the music of Super Sentai.