Does the Lyre of Building require a Perform (Stringed Instruments) skill check for all uses?

Question

The Lyre of Building has the following description:

This magical instrument is usually made of gold and inlaid with numerous gems. If the proper chords are struck, a single use of this lyre negates any attacks made against inanimate construction (walls, roof, floor, and so on) within 300 feet. This includes the effects of a horn of blasting, a disintegrate spell, or an attack from a ram or similar siege weapon. The lyre can be used in this way once per day, with the protection lasting for 30 minutes.

The lyre is also useful with respect to building. Once a week, its strings can be strummed so as to produce chords that magically construct buildings, mines, tunnels, ditches, etc. The effect produced in 30 minutes of playing is equal to the work of 100 humans laboring for 3 days. Each hour after the first, a character playing the lyre must make a DC 18 Perform (string instruments) check. If it fails, she must stop and cannot play the lyre again for this purpose until a week has passed.

It lists the DC 18 Perform (Stringed Instruments) check for the quick-building ability. Does that also apply to its ability to negate attacks against inanimate construction, or would that require a UMD check?

Answer 1

No

Only the uses that list a perform check require one. 'The proper chords' are equivalent to a command word. If you know the command (chords), then no UMD check is needed.

Answer 2

Only the second part of the quick build ability states the need to make a perform check. Thus only then do you need to make it.

This magical instrument is usually made of gold and inlaid with numerous gems. If the proper chords are struck, a single use of this lyre negates any attacks made against inanimate construction (walls, roof, floor, and so on) within 300 feet. This includes the effects of a horn of blasting, a disintegrate spell, or an attack from a ram or similar siege weapon. The lyre can be used in this way once per day, with the protection lasting for 30 minutes.

No check is mentioned and non is needed.

The lyre is also useful with respect to building. Once a week, its strings can be strummed so as to produce chords that magically construct buildings, mines, tunnels, ditches, etc. The effect produced in 30 minutes of playing is equal to the work of 100 humans laboring for 3 days.

Again, no check needed

Each hour after the first, a character playing the lyre must make a DC 18 Perform (string instruments) check. If it fails, she must stop and cannot play the lyre again for this purpose until a week has passed.

Now it stated that if you keep playing for longer than one hour you need to succeed on the check and repeat it once per hour.

So playing the lyre to protect your building doesn't need to make a check, nor does playing it to activate the fast building for the first hour. Only if you want to get more fast building than one hour's worth (100 humans labouring for 6 days) makes it necessary to succeed on the check.