Sometimes we allow ourselves to live under the illusion that lawyers know what they are doing. Well of course they don't. If they did, they would have nothing to argue over, and no business. So one lawyer exploits the errors of another, who in turn fights back, and at the end of the process they both go away with shedloads of money, paid by their clients largely for their mistakes.
So there is no such thing as a watertight contract. The flowery and excessive language used by lawyers prevents that, as does their obsession for writing extraordinarily long sentences entirely without commas.
Very few disputes in the music industry go all the way through the legal process. Usually the big guy threatens the little guy, the little guy realizes that he is bound to lose and gives in. This unfortunately has the effect of perpetuating bad practices in the drafting of contracts, since they are rarely properly tested in court.
One example recently seen was a contract for a composer to write and record tracks for a TV series. The composer was paid a substantial sum of money to buy out all the rights to the music, apart from the performance right for which he will continue to be paid every time the program is broadcast.
However there was a serious defect in the contract. It only specified that the deal was for the music; it said not one word about the recordings the composer had made.
There is a completely separate copyright in a recording, independent of the music. So if you write and record your own music, you can license or sell either or both copyrights in your work. In practice it would nearly always be both.
However, since this particular contract said nothing about the recordings, the composer would have been within his rights to say that they were merely demo recordings and could not be used in the program. The production company would then have had to re-record the music.
Apparently the contract was checked by a music business lawyer, who really should have spotted this.
In practice, since the composer wants to continue working and not tick anyone off, he will probably just hand over the recordings, overlooking the omission in the contract.
The best practice with contracts is to treat them as a written down expression of what both parties genuinely believe they are agreeing to. And contracts should be written in plain English – there is no need for them not to be. If both parties fully understand what they are agreeing to, and a competent music lawyer has checked that all details have been accounted for, that will lead everyone to the greatest possibility of mutual success.