I have come across these tapes a few times at the thrifts.  They are accompaniment tapes that have the instruments and background vocals.  Just add lead vocals!  Most of the titles that I have found have been aimed at the church crowd but there could be others.  Put out under the "Studio Series" name and marketed by Word, Inc.  

The tapes themselves are only a few minutes in length I would guess.  Enough for one song or more.  They sound kind of warbly playing on my hi-fi and on my boombox.  Is this common to these kinds of tapes?  I think I have heard that complaint before with the reel clear tapes.

Well they look cool at least 

Would you mind buying few and mailing it across the continents?

i would imagine if you was to try the big brand name reel tapes they would'nt warble.

TEAC,PIONEER, BASF, these are the quality ones.

i have the cheap no name ones and the cheap eagle ones they just look good in a box