Swiss Travel Pass/Half Fare Card or Swiss Travel Pass Flex

You need the 4-day Flex Pass. This covers four days of travel within a month. Any four days, your choice.

The regular 4-Day Swiss Pass is indeed good for four consecutive days only. It doesn’t matter is you ride a train every day or not: the pass is invalid after those four consecutive days. Say you start your pass on June 1. You can use it for travel on June 1, 2, 3, and 4 only. It is not good after that.

With a Flex Pass, if your first day is June 1, you can use it for three more days of your choice in the 30 day period of validity.

If you get a Flex Pass make SURE you enter the date of travel in the box provided on the pass BEFORE you board the first traini of the day. If your journey includes multiple trains that same day they are all covered.

There is a long thread in General Europe by someone who neglected to do this and the consequences were fairly bad. He blamed “Eurail” but the fault was fully his own for not complying with the Conditions of Use.

Yes, 4 consecutive days means that. If the pass starts on Monday, your four days are Monday, Tuesday, Wednesday and Thursday. You don't have to travel every day, but you are wasting a day of your pass if you don't.
The alternative is a "Flex" pass, when you have a choice of any 4 days, not necessarily consecutive. This costs slightly more.

The passes are all listed here: https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/international-guests/swiss-travel-pass.html

Swiss Travel Pass 3 days CHF 225 2nd class, CHF 358 1st class
Swiss Travel Pass 4 days CHF 270 2nd class, CHF 429 1st class
Swiss Travel Pass 8 days CHF 398 2nd class, CHF 631 1st class
Swiss Travel Pass 15 days CHF 485 2nd class, CHF 765 1st class

Swiss Travel Pass Flex 3 days in 1 month CHF 259 2nd class, CHF 412 1st class
Swiss Travel Pass Flex 4 days in 1 month CHF 310 2nd class, CHF 493 1st class
Swiss Travel Pass Flex 8 days in 1 month CHF 445 2nd class, CHF 706 1st class
Swiss Travel Pass Flex 15 days in 1 month CHF 532 2nd class, CHF 840 1st class

thank you all for your quick responses. Our itinerary is:
Arrive Zurich - train to Lucerne for two days (we will just pay the $20 or so and NOT activate the pass there)
Lucerne to Montreaux - activate pass plus make reservations for Panorama train. This would be day 1 of the 4 day pass
Montreaux to Geneva - Day 2 of the pass
Montreaux to Wengen - Day 3 of the pass
Wengen to Salzburg - Day 4 of the pass
All of this will be within the 10 days we are in Switzerland.

The last question is - does the Swiss Travel Pass include the 50% off of buses, museums and boats on the days that you are NOT on a train?

thanks so much

The Swiss Travel FLEX Pass for the 4 days out of your 10 days in Switzerland does NOT cover anything on the days that aren't counted as TRAVEL days. It makes no difference whether you use it on a train, bus, boat or museum, each date used counts as a TRAVEL day.

mariaklau, FYI, Zürich Flughafen (airport) to Luzern is CHF 30. According to Google, that converts to USD 31,27 at today's rate.

The pass is valid on all transport, including city transport, on the 4 days you select. So, for example, you could use city buses and trams in Luzern, Montreux and Geneva, but only on the 4 days you have filled in on your pass.

Montreux to Geneva costs CHF 31--about the same as Zürich airport to Luzern (CHF 30). So you might not want to use a Pass travel date for that day, either (Day 2 of the pass), just like you don't plan to use one of your pass dates for your trip from Zürich airport to Luzern.

LindaL has a good point. The 31 CHF fare from Montreux to Geneva is not worth covering with a "Pass day", as these are 77 CHF each with the 4-day Flex. You could get by with a 3- day Flex for 259 CHF, unless you want the flexibility to travel somewhere else as a daytrip.

You also asked about the Half Fare Card. I calculate you save more money with that.
Zurich airport to Luzern 30 CHF
Luzern to Montreux via Zweisimmen, 77 CHF
Montreux to Geneva and return, 62 CHF
Montreux to Wengen, 89.40 CHF
Wengen to Buchs SG (on the way to Salzburg), 111.40 CHF

That totals out to about 370 CHF, with a Half Fare Card costing 120 CHF, your total out-of pocket is 305 CHF (185 + 120), 35 CHF less than the 340 CHF for a 310 CHF 4 day flex pass plus the 30 CHF for the Zurich airport to Luzern leg.

In addition, you will get 50% off all tickets for the entirety of your trip. Mountain lifts, city trams, boat trips, everything.

You might also look to buy a nonrefundable discount tickets from Zurich to Salzburg on the direct Austrian Railjet Train. Discounts will often trump any discounts you receive with a pass or Half Fare Card.