Is it permissible to have a musical Friday night Kabbalat Shabbat service with instruments in the summer months (before Shkiah) and light candles afterwards, or must all instruments be removed before Mizmor Shir, or is the entire concept not in keeping with Halacha and why?

Shalom, Thank you for your question. As you know musical instruments are forbidden to be used on Shabbat. The first question is at what point of the service does Shabbat come in? Assuming that service is before sunset (as you write in your question) then musical instruments will become forbidden when saying the last verse of Lecha Dodi – Boi BeShalom. (See Shulchan Aruch, Orech Haim, 261 Mishna Brurah 31). Based on this, theoretically musical instruments could be used up to that point, then put away before the last verse of Lecha Dodi. However, there are good reasons why this is not the accepted practice. In general the use of musical instruments in synagogue services is problematic. There is much discussion in halachic literary about this issue – especially after the Reform movement in Germany started using an organ. But even if we put this issue aside (and a case may be made to allow the use of instruments on a weekday – on our hebrew site there is a long response about this issue which quotes the opinions of many Rabbis who allow musical instruments when this does not break Shabbat or Yom Tov), there is still a possible educational problem. Using the instruments during kabalat Shabbat may lead to people mistakenly playing on Shabbat. One can imagine a case where the minyan was running a bit late and music played after sunset. Or where one musician forgot and kept playing after Lecha Dodi. Or where someone of lesser Jewish learning went and started playing an instrument during their own kabalat Shabbat service (when camping or by themselves) and didn't know the restrictions of time and place in the service. For these reasons the ultimate ruling on this issue will have to come from your local Rabbi who is familiar with the particular community and situation. In the event that there is no Rabbi to rule for your particular case, then my advice would be to refrain from using instruments during kabalat Shabbat at all – and continue the normative practice of just singing (and dancing if you so choose). Many Blessings.