A man has been caught playing the trumpet as he drove over the West Gate Bridge.

Highway patrol officers received numerous reports of a black Toyota sedan driving erratically towards the city about 12.20pm on Friday.

Senior Constable Adam West said officers pulled alongside the vehicle and were shocked to discover the motorist mid-song.

The 27-year-old bugle boy from Portarlington was fined $354 for careless driving.

No word on what he was playing.