By Phoenix Tso

LOS ANGELES (Reuters) - A musical riff Led Zeppelin is accused of stealing from another band for its 1971 classic "Stairway to Heaven" was not unique, singer Robert Plant and guitarist Jimmy Page's attorney said at a civil trial on Tuesday.

"No one owns common musical elements," defense attorney Peter Anderson said in opening arguments for the copyright infringement trial in Los Angeles federal court.

The lawsuit, which alleges the British band stole the opening chords for "Stairway to Heaven" from the 1967 instrumental "Taurus" by the American band Spirit, was brought by Michael Skidmore, a trustee for the late Randy Wolfe, Spirit's guitarist and the composer of "Taurus."

"Stairway to Heaven" is considered one of the most widely heard compositions in rock history and is the signature song of Led Zeppelin, which broke up in 1980.

The case comes just over a year after a federal jury in Los Angeles found recording stars Robin Thicke and Pharrell Williams had plagiarized Motown great Marvin Gaye in creating their hit single "Blurred Lines," and awarded Gaye's family $7.4 million.

In the latest case, Plant, 67, and Page, 72, appeared in court on Tuesday sporting long gray hair and are expected to testify eventually in the closely watched trial.

Skidmore has said Page may have been inspired to write "Stairway" after hearing Spirit perform "Taurus" while the bands toured together in 1968 and 1969, but that Wolfe never received credit.

Wolfe, also known as Randy California, drowned in the Pacific Ocean in 1997.

U.S. District Judge Gary Klausner said in April that a jury might find "substantial" similarity between the first two minutes of "Stairway" and "Taurus," and to let it decide whether Plant and Page were liable for copyright infringement.

Attorney Francis Alexander Malofiy, representing Skidmore, told a jury in opening arguments the case centers on an infringement by Led Zeppelin of copyright law, which protects artistic creation.

"It gives credit to creation but it does not give credit to copying," Malofiy said.

Anderson said his side will present evidence showing neither Skidmore nor Wolfe's trust own the copyright to "Taurus."

Testimony in the case began with Janet Wolfe, sister of Randy Wolfe, who said her brother had written "Taurus" for his wife, Robin.

When asked if she and her brother had ever discussed "Stairway to Heaven," Janet Wolfe said yes.

"It was something that upset him for many, many years," she said.

(Additional reporting by Paula Lehman, Alex Dobuzinskis and Piya Sinha-Roy in Los Angeles,; Editing by Simon Cameron-Moore and Matthew Lewis)