How do you judge when a collaboration works? Increasingly, artists have been moved to work with others from different fields in an attempt to reach a different audience or to gain inspiration in the process. In this case, however, Ancient Future is an example of two like minds working together to create something beautiful, which also fits perfectly within each musician's body of work.

Christopher Willits is a guitarist and electronic pioneer from San Francisco who has previously worked with the likes of Matmos, and Ryuichi Sakamoto is a composer and pianist from Tokyo who is most well known for award winning film scores such as Merry Christmas Mister Lawrence and the Last Emperor, as well as being a founding member of the Yellow Magic Orchestra.

Ancient Future is their second album together, following on from 2008's Ocean Fire. The six tracks here are completely instrumental and were created from piano pieces which Sakamoto had sent to Willits, who then did more electronic work on them. Willits has developed his own software which manipulates his guitar sounds and enables him to create rich textures and harmonies. There are echoes of the music Sakamoto has made with Christian Fennesz, but Willits's guitar style and overall sound helps distinguish this as something different.

Whilst this is definitely an experimental album it is also a very quiet ambient one, and on my first few plays I tried to listen on trains and buses but I was unsure where the music stopped and the outside world began. I came to the conclusion that Ancient Future is best heard late at night when everything else is quiet.

Opening track 'Reticent Reminiscence' shows the diverging elements straight away. Sakamoto’s pretty piano chords are sustained and hang in the air, whilst Willits has manipulated them and created a subtly harmonic underscore.

'Abandoned Silence' hints at a very ambient kind of jazz with its extended chords and guitar parts, whilst the shifting background of 'I Don't Want to Understand' is first suggestion of rhythm. 'Levitation' is a cold bleak piece created around gentle feedback, although it turns into the more playful 'Releasing' which is more delicate harmonies and gentle guitar runs.

Closing piece 'Completion' is appropriately named, as it is where it all comes together. All the parts have converged into a beautiful ambient piece, and the album ends on this still, tranquil note.

At 32 minutes in length, it feels quite brief, especially as the tracks merge so well together, but to make it any longer would have just been extending it for the sake of it. In a way, Ancient Future is a musical exploration of the very art of collaborating itself, as it works with its divergent parts in an interesting way and ends up creating something worthwhile and often quite beautiful.