The orchestra has recorded a track for Teenage Cancer Trust and has already played a gig at the Royal Albert Hall.
The song, called Six O'Clock, was written by Richard Watson and features Mike Rutherford (Genesis) playing the 'clutch guitar' and Kenney Jones (The Who) playing the 'wheel drums'.
Musicians from both The Academy of Contemporary Music in Guilford and the National Symphony Orchestra make up the other band members.
The track is downloadable from www.timesonline.co.uk/carparts and a link to the Teenage Cancer Trust allows listeners to make a donation.
Band members from Travis played the Focus instruments live on stage at the Royal Albert Hall last week during the annual Teenage Cancer Trust gigs.
Supporting the headline act - The Fratellis - Neil Primrose and Andy Dunlop from Travis, accompanied by musicians from the National Symphony Orchestra, performed two tracks including the charity single.
A national exhibition tour, featuring the Focus car-part instruments from the TV ad, will take place at The Hospital, Covent Garden in London from the April 17 to 19, the Fruit Market in Glasgow from April 24 - 26 and St George's Hall in Liverpool from the May 9 - 11.
The exhibitions, which are free, open from 11.00 to 6pm daily and there will be live performances on the car part instruments at 1.15pm and 5.15pm.
A spokesman said: "The tour was inspired by public doubts that the instruments were real and that they were used to perform the music featured in the TV commercial."
Here's the original advert: