So here's the thing: As a Bard you can make use of some very powerful spells with instruments, but in combat you have only access to the 8 you have selected for your personaly inventory.

There are 21 instruments in the game (excluding imports), so you have to make some decisions.

I have structured this by the music skill required to use the instruments, which also roughly reflects the order in which you usually find them:

MUSIC SKILL <= 30
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Bard inventory:
- Poet's Lute (Sleep)
- Angel's Tongue (Bless)
- Piering Pipes (Shrill Sound)
- Siren's Wail (Insanity)
- Snare of Delay (Slow)
- Frigid Fiddle (Freeze Flesh)
- Silent Lyre (Silence)
Party inventory:
- Viola D'Amore (Charm)
- Mandolin of the Magus (Magic Screen)

MUSIC SKILL <=60
===============
Here the choices are rather straightforward. Sleep is not as powerful anymore, neither are attacking spells like Shrill Sound. Instead of Slow you now have Haste, which is better, and instead of Freeze Flesh you have Freeze All. The only tough call is whether or not to discard Silence, but I figure in W8 this spell is not as powerful anymore compared to its importance in W6/7, so I got rid of it. But it probably also depends on what your real spell casters can do.
Bard inventory:
- Angel's Tongue (Bless)
- Siren's Wail (Insanity)
- Jericho Horn (Armormelt)
- Rousing Drums (Haste)
- Soulful Sax (Soul Shield)
- Arresting Aria (Freeze All)
- Banshee's Howl (Hex)
- Dulcimer of Mending (Heal All)
Party inventory:
- Viola D'Amore (Charm)
- Mandolin of the Magus (Magic Screen)
Discarded:
- Poet's Lute (Sleep)
- Piercing Pipes (Shrill Sound)
- Snare of Delay (Slow)
- Frigid Fiddle (Freeze Flesh)
- Silent Lyre (Silence)

MUSIC SKILL >60
===============
Here the "problems" start. By level 90 you can additionally use the follwing instruments:
- Succubus Song (Lifesteal)
- Chaos Drone (Pandemonium)
- Strings of Seduction (Turncoat)
- Hades Harp (Cerebral Hemmorage)
- Renaissance Lute (Restoration)
- Infernal Horn (Nuclear Blast)

So, which of those do you add to your inventory, and which of the old ones do you discard? Again, it probably depends on what kinds of magic users you have, and also of the area you're in (Nuclear Blast is not really helpful against Rapax).

Personally I don't really use Lifesteal. Pandemonium sounds nice, but I rerely use it either (not a big fan of the Fear condition, since enemies tend to run away and hunting them down can be a drag). Turncoat is REALLY nice and works like an alternative of Summon Elemental, since you essentially create a new temporary ally. Cerebral Hem. is a very good attack vs. single opponents (around 100 damage is quite common). Restoration is always nice, but if your party has very good resistances, you might not use it very often. Nuclear Blast is a cool damage spell, but not as powerful as in earlier Wizardry games.

What are your preferences?


PS: The same issue occures for the Gadgeteer of course, but I think that it's a bit more obvious (not super obvious though) which gadgets to keep and which to discard.

I don't really have input since I didn't take a bard with me on my play through but I will save this for future use thanks for your work and for caring enough to post it.

Some notes:

The Soulful Sax is, I believe, an RPC's prized possession, so you aren't going to keep it without an exploit.

The Banshee's Howl isn't worth using, as Hex is rather underpowered for its level. The Frigid Fiddle is likely to be more useful, as it can affect enemies you can't see. Alternatively, keep the Piercing Pipes so that you retain an offensive option (unless you have the Horn of Prometheus, of course).

At high levels, note that effects that target enemies suffer from having to get past the enemies' resistances, which is a problem because instruments can't benefit from Power Cast. The Renaissance Lute is nice because it can restore stamina as well as healing and removing status ailments; at high levels, I believe a bard can restore her own stamina this way. Turncoat is useful against enemy summons, who have high HP but low resistances. Unfortunately, Bards don't get any instant death attacks, which are what you *really* want in the big encounters.

Also, consider the weight of the instruments. The Silent Lyre, in particular, is not worth its weight. (That can also be said of the Lyre of Cakes, since there are two Dulcimers of Mending, which do the same thing and are much lighter, therefore making the Lyre of Cakes not worth importing.)

- Piercing Pipes (Shrill Sound)
Not that bad... I keep it until about level 15 then pass it over to Sax... his level tends to be less so this is a good anti-group option for him.

- Chaos Drone (Pandemonium)
Hits every bad guy in range and doesn't give a fig if they are blocked, in one pack or lots of small groups. Will put fear in Rapax Samurai or turn magic resist golums burko... what's not to like?

What's not to like? For one thing, it can only hit visible enemies. This makes it significantly less useful in areas like Rapax Castle where there are lots of walls. (Group targeted spells like Freeze Flesh work better in this situation.) The other is that afraid enemies will run away, which is extremely annoying as it is a pain to chase down such enemies. (It's why I find spells like Terror and Blinding Flash to be of limited use, useful only to give yourself a little breather and not when you are trying to win the battle quickly.)

As far as gadgets are concerned, the Holograph Projector (Guardian Angel) is surprisingly useful, despite it appearing rather late for a second level spell. When a character is injured, Guardian Angel is useful as it is a nice substitute for healing and isn't wasted if the character is healed first. Also, the Port-o-Potty casts Noxious Fumes, which I actually prefer to Fireball.

"Discarded"
From personal inventory or also from party inventory?

No need for an exploit to get the Soulful Sax, can be stolen(to get 2 instances with exploit;) and its a 100% drop.

I never use slow, nearly ineffective and last not least doubles anim time, makes combat vs many much longer(=boring)
Similar for pandemonium because they run in fear, although its rather effective as last resort.

Turncoat: only 1 foe with chance to completely negate effect with a saving throw, and i still have to kill him some turns later?
The time foes are still threatening enough for that, the party most likely has no access to turncoat

Turncoat is quite useful against enemy summons; the elementals are low level and have low resistances (but have lots of HP and hit hard), and the summons have a finite duration, so you can avoid killing them if enough time passes.

Dust of Defection casts Turncoat and doesn't have a level requirement, so it can be used when enemies are still threatening.

Also, keep in mind that enemies will also attack the target of Turncoat, so your characters don't get attacked as much.

I'm currently trying out the 4-character party of only the 4 non-caster specialists, and once again this issue comes up.

Currently I possess:
- Angel's Tongue
- Piercing Pipes
- Siren's Wail
- Banshee's Howl
- Rousing Drums
- Mandolin of the Magus
- Jericho Horn
- Silent Lyre
- Soulful Sax (stolen from Saxx)
- Arresting Aria
- Dulcimer of Mending
- Chaos Drone

I've already sold:
- Viola D'Amore (my Music is already >90, and training with Charm is a pain in the ass)
- Snare of Delay (sort of obsolete once you have the Rousing Drums)
- Poet's Lute (not very usefull anymore)
- the other Silent Lyre

Now, one thing that really is a problem with this very party is encumbrance. Except for the Rogue everyone has a ranged weapon burning tons of ammo (especially the Gadgeteer with the upgraded Omnigun and my Fighter with the Tripleshot Crossbow), so I need to carry around at least 100-200 Stones, Bolts, ect. Then of course Gadgets and Instruments also weigh a lot, and I need to carry along a lot of potions (mostly Hv. Stamina and Restoration) and some bombs etc.

So Weight is an issue. If I now check the weight of the different instrument types, someting really stands out:
- Horns: weight 2
- Violins: weight 3
- Lutes, Bagpipes, Sax: weight 4
- Drums: weight 7
- Harps: weight 18 (!)

Harps are REALLY heavy. And if I look at the Harps out there (Silent Lyre, Succubus Song, Hades Harp), it's a bit underwhelming, especially for this very party. Single-target attack spells might have their use if your Bard has no ranged weapon, but in this case my Bard is almost exclusively trained in ranged combat. The Silent Lyre might be not bad, but I feel that the spell Silence is much worse than in W6/W7, since casters usually have higher resistances than combat-type monsters. So no Harps.

As for the other instruments, here's a quick (re-)assessment:

- Angel's Tongue: The higher your level gets, the less useful this is, since Bless adds a fixed bonus (I think it's +4 AC, +2 To Hit), which is of course better if you have 5 AC rather than 20 AC. It's still very good, but often I don't find the time to cast it, since Haste and/or some spell targeted at opponents seems more important.

- Piercing Pipes: I probably soon dump this one, since the damage dealt gets more and more underwhelming, and I don't really need a lot offensive magic in this party (and if I do, my Gadgeteer can cover this).

- Siren's Wail: Still very useful - Insanity is one of the best spells you can harass your opponents with (some at least). It too gets resisted more and more, but currently it's still useful.

- Banshee's Howl: I'm not entirely sold on Hex, though it's probably a very good spell. The thing is, you don't actually SEE a real effect - monsters don't attack each other, they don't skip turns or take damage. They are just worse overall than before. I guess it's useful, but I very rarely cast it. Also it gets resisted by a lot of opponents, so I probably will dump this one as well.

- Rousing Drums: It is a drum (so quite heavy), but Haste is one of the best buffs out there (at least if you have not invested heavily in Speed anyways), so I will keep it.

- Mandolin of the Magus: In the party inventory; great to have.

- Jericho Horn: As far as supporting spells go, I think Armormelt is one of the best even until late, mainly because opponents usually don't resist it. So this one I keep (it's also a Horn, so it's lightweight)

- Silent Lyre: As I've said above, I'll probably sell the second one as well. Ultra-heavy and rarely uselful.

- Soulful Sax: Soul Shield is great of course if you need it, but most of the time this will be dead weight. So I think I keep it in the party inventory and switch to it if I see an opponent with Divine/Mental magic.

- Arresting Aria: Great spell, which will become especially useful in the Rapax areas (Water realm). I think once I get the Frigid Fiddle (I've not been to Mt. Gigas yet), I will use this one for a while (higher level, higher reliability, less stamina drain) and maybe switch to the Aria in the late game again.

- Dulcimer of Mending: I'm not sure yet whether my Bard, my Gadgeteer, or both keep the Heal All device in their personal inventory, because in the majority of the cases I heal my party after fights. One guy should have this ready to use in battles of course, but right now I'm sure who.

- Chaos Drone: Pandemonium has very limited uses (I'm counting three: If you get overrun, in dedicated ranged parties where you want to avoid melee combat, and as a tactical follow-up to Cloud spells), so I think I'm going to sell it. It's also very expensive, so I'm getting a good price.

As for the instruments I'm still going to get, the most important one is the Renaissance Lute, which I think will have in my personal inventory instead of the Dulcimer (Heal All will be covered by the Gadgeteer). I might add the Infernal Horn as well, but probably dump the Strings of Seduction, Succubus Song, and (as already said) the Hades Harp.

So in the end my inventory will be:
1. Renaissance Lute
2. Infernal Horn
3. Frigid Fiddle / Arresting Aria
4. Soulful Sax / Hv. Stamina Potion
5. Jericho Horn
6. Rousing Drums
7. Siren's Wail
8. Angel's Tongue

I don't know... Although I hardly ever used it before my solo mage used it against the Rapax to quite some success as it turns an enemy into a guardian (she couldn't really fight even a single Rapax in melee w/o potions). Also it came in quite handy to turn Crystal Unicorns @ Ascension Aeak (arrived around level 24) which promptly gave me a level 7 magic screen to last for about all of Ascension Peak ^^

So far I've not played the bard outside of regular full parties so I don't know about the inventory but I'd dump a lot before I'd dump instruments. Weight makes for the sole reason and that's not too much of a factor apart from harps (& drums perhaps but that's settled: slow dumped, haste kept). I am not a fan of silence so I could see me dumping that to lighten my inventory. The other two make up a lot of your spell damage. It's mental & divine realm and high level spells at that so unless your Bard doesn't need spell damage at all I'd want to keep those.
With a variety in my inventory I'll reequip a lot for specific fights / areas. E.g. Turncoat is rather specific so I'd only keep it in the bards inventory while expecting opponents I want to use it against. That's the case for the majority of instruments I'd say.

Only Restoration, Haste and Heal All are pretty much always useful. Armormelt is always applicable but rarely outstanding and Magic Screen is cast from party inventory. The others depend on various factors, not least the opponents' resistances.

One more thing to consider:

It seems that, in order to eliminate the fizzle/backfire chance, two requirements need to be met:
1. Level needs to be 6 more than the minimum required to use the instrument/gadget
2. Music/Engineering must be around 50 + 10 * level of spell.

For the Dulcimer of Mending, for example, you need level 17 and around 90 skill. From testing, 90 seems to be enough, but 80 is definitely not.

For the Renaissance Lute, it looks like you need level 24 and around 110 music. That, of course, requires the Puck's Cap (dropped by Higardi bandit types). Unfortunately, there's no similar item for Gadgeteers.