How much can a musician borrow from another person’s music in his or her own song?

How much can a musician borrow from another person’s music in his or her own song?
Music is extremely difficult in copyright law, because anyone who plays music knows it is as much collage work as any art form. And we all, as listeners, have the experience of listening to an artist and "hearing" the artists who have influenced that artist come through in the music.
What one person might call theft, another may call inspiration. One musician might say another is influenced by another's style, while another might say that he is ripping off that style. Incorporating someone's chord progressions or musical stings into your own song might be seen as pastiche or parody, but they also might be seen as a sort of theft.
For example, more than one rap feud has been started by one rapper outright copying or subtly duplicating another rapper's lines in his own music.
On Jay-Z's debut album Reasonable Doubt, producer Ski used a vocal sample from Nas' "The World Is Yours" as the chorus to his song "Dead Presidents." After a feud erupted between the two, stealing and parodying each others’ verses was a regular feature of their songs: "So yeah I sampled your voice, you was using it wrong / You made it a hot line, I made it a hot song." 
Jay-Z, now one of the most successful musicians of all-time, has made a 14-year career on outright copying word-for-word dozens of unique lines and couplets from other artists.
Borrowing from an already created work may be entirely unintentional or subconscious. Take, for example, the process of two songwriters writing together for the first time: 
“When Tim played the aforementioned chord sequence of E minor, C major, A minor7, and B major, Bradley's initial reaction was a shaking of the head, followed by ‘Leonard Cohen could sue you for that.’ He indicated the chord sequence was from Cohen's ‘Famous Blue Raincoat’, which he proceeded to play and sing. "It is…I didn't realise ... how lame of me." Bradley then went on to change the chord sequence, adding some ‘originality.’ ” [ Peter DeVries, The Rise and Fall of a Songwriting Partnership]
In a real-life example, in 2010 folk singer Jake Holmes sued Led Zeppelin guitarist Jimmy Page over a song Holmes recorded in 1967 called “Dazed and Confused.” Led Zeppelin recorded a similar-sounding song of the same name in 1969.

Now let’s explore that situation. For one thing, to conclude that Led Zeppelin’s song is copyright infringement based on a 30-second sound clip is ridiculous. But, if someone got an expert to analyze the two songs and look at the similarity between the notes and song structure, they could determine if the songs are similar enough to be considered the same. Conversely, even though it definitely wouldn't be the first time Led Zeppelin borrowed wholesale from another band (it's common knowledge that Led Zeppelin took guitar lines and lyrics from other songs), that's also the nature of blues rock music—especially blues rock music in the 1960s, when bands were more limited by popular tastes as to what they could do.
As far as the law is concerned, the line for whether a particular musical expression is considered copying of a musical idea or an expression is particularly gray and often depends on the particular facts of the case.
Generally, a court analyzes the case to look for two things: proof of access to the work and proven similarity. Moreover, if you can make one of the two elements abundantly clear, this lessens the need to satisfy the other one. 
If you are musician with questions about whether specific songs of your would be deemed infringing, feel free to contact New Media Rights via our contact form to find out whether you qualify for free or reduced fee legal services. We also offer competitive full fee legal services on a selective basis. For more information on the services we provide click here.
Find additional articles by