"Love Is Blue" is a good song. Was it a Harpsichord?
There were several instrumentals on the charts in the 70's. "Rockford Files", "Star Wars" and my favorite, "Tubular Bells". "Tubular Bells" was actually a continuous song that lasted the length of an album by Mike Oldfield. One of my favorite "stoner" albums from the 70's.

Two excellent instrumental albums by Frank Zappa, "Hot Rats" includes what I think was his best instrumental, "Peaches In Regalia" and his album "The Grand Wazoo", a jazz album.